Introduction to Java Programming, 4E

Introduction to Java Programming, 4E
First Class: Introduction, Prerequisites, Advices, Syllabus Lab 1: Create a Java Project, Compile, and Run. Show syntax errors Print program Capture screen shots, and save it in Word, and print it. Homework One: Check in the class randomly. Y. Daniel Liang

Introduction Course Objectives Organization of the Book

Course Objectives Upon completing the course, you will understand
Create, compile, and run Java programs Primitive data types Java control flow Methods Arrays (for teaching Java in two semesters, this could be the end) Object-oriented programming Core Java classes (Swing, exception, internationalization, multithreading, multimedia, I/O, networking, Java Collections Framework)

Course Objectives, cont.
You will be able to Develop programs using Forte Write simple programs using primitive data types, control statements, methods, and arrays. Create and use methods Develop a GUI interface and Java applets Write interesting projects Establish a firm foundation on Java concepts

Book Chapters Part I: Fundamentals of Programming
Chapter 1 Introduction to Java Chapter 2 Primitive Data Types and Operations Chapter 3 Control Statements Chapter 4 Methods Chapter 5 Arrays

Book Chapters, cont. Part II: Object-Oriented Programming
Chapter 6 Objects and Classes Chapter 7 Strings Chapter 8 Class Inheritance and Interfaces Chapter 9 Object-Oriented Software Development

Book Chapters, cont. Part III: GUI Programming
Chapter 10 Getting Started with GUI Programming Chapter 11 Creating User Interfaces Chapter 12 Applets and Advanced GUI

Book Chapters, cont. Part IV: Developing Comprehensive Projects
Chapter 13 Exception Handling Chapter 14 Internationalization Chapter 15 Multithreading Chapter 16 Multimedia Chapter 17 Input and Output Chapter 18 Networking Chapter 19 Java Data Structures

Chapter 1 Introduction to Java and Forte
What Is Java? Getting Started With Java Programming Create, Compile and Running a Java Application

What Is Java? History Characteristics of Java

History James Gosling and Sun Microsystems Oak
Java, May 20, 1995, Sun World HotJava The first Java-enabled Web browser JDK Evolutions J2SE, J2ME, and J2EE (not mentioned in the book, but could discuss here optionally)

Characteristics of Java
Java is simple Java is object-oriented Java is distributed Java is interpreted Java is robust Java is secure Java is architecture-neutral Java is portable Java’s performance Java is multithreaded Java is dynamic

JDK Versions JDK 1.02 (1995) JDK 1.1 (1996)
Java 2 SDK v 1.2 (a.k.a JDK 1.2, 1998) Java 2 SDK v 1.3 (a.k.a JDK 1.3, 2000) Java 2 SDK v 1.4 (a.k.a JDK 1.4, 2002)

JDK Editions Java Standard Edition (J2SE)
J2SE can be used to develop client-side standalone applications or applets. Java Enterprise Edition (J2EE) J2EE can be used to develop server-side applications such as Java servlets and Java ServerPages. Java Micro Edition (J2ME). J2ME can be used to develop applications for mobile devices such as cell phones. This book uses J2SE to introduce Java programming.

Java IDE Tools Forte by Sun MicroSystems Borland JBuilder
Microsoft Visual J++ WebGain Café IBM Visual Age for Java

Getting Started with Java Programming
A Simple Java Application Compiling Programs Executing Applications

A Simple Application Example 1.1
//This application program prints Welcome //to Java! package chapter1; public class Welcome { public static void main(String[] args) { System.out.println("Welcome to Java!"); } Source Run NOTE: To run the program, install slide files on hard disk.

Creating and Compiling Programs
On command line javac file.java

Executing Applications
On command line java classname

Example javac Welcome.java java Welcome output:...

Compiling and Running a Program
Where are the files stored in the directory?

Anatomy of a Java Program
Comments Package Reserved words Modifiers Statements Blocks Classes Methods The main method

Comments In Java, comments are preceded by two slashes (//) in a line, or enclosed between /* and */ in one or multiple lines. When the compiler sees //, it ignores all text after // in the same line. When it sees /*, it scans for the next */ and ignores any text between /* and */.

Package The second line in the program (package chapter1;) specifies a package name, chapter1, for the class Welcome. Forte compiles the source code in Welcome.java, generates Welcome.class, and stores Welcome.class in the chapter1 folder.

Reserved Words Reserved words or keywords are words that have a specific meaning to the compiler and cannot be used for other purposes in the program. For example, when the compiler sees the word class, it understands that the word after class is the name for the class. Other reserved words in Example 1.1 are public, static, and void. Their use will be introduced later in the book.

Modifiers Java uses certain reserved words called modifiers that specify the properties of the data, methods, and classes and how they can be used. Examples of modifiers are public and static. Other modifiers are private, final, abstract, and protected. A public datum, method, or class can be accessed by other programs. A private datum or method cannot be accessed by other programs. Modifiers are discussed in Chapter 6, "Objects and Classes."

Statements A statement represents an action or a sequence of actions. The statement System.out.println("Welcome to Java!") in the program in Example 1.1 is a statement to display the greeting "Welcome to Java!" Every statement in Java ends with a semicolon (;).

Blocks A pair of braces in a program forms a block that groups components of a program.

Classes The class is the essential Java construct. A class is a template or blueprint for objects. To program in Java, you must understand classes and be able to write and use them. The mystery of the class will continue to be unveiled throughout this book. For now, though, understand that a program is defined by using one or more classes.

Methods What is System.out.println? It is a method: a collection of statements that performs a sequence of operations to display a message on the console. It can be used even without fully understanding the details of how it works. It is used by invoking a statement with a string argument. The string argument is enclosed within parentheses. In this case, the argument is "Welcome to Java!" You can call the same println method with a different argument to print a different message.

main Method The main method provides the control of program flow. The Java interpreter executes the application by invoking the main method. The main method looks like this: public static void main(String[] args) { // Statements; }

Displaying Text in a Message Dialog Box
you can use the showMessageDialog method in the JOptionPane class. JOptionPane is one of the many predefined classes in the Java system, which can be reused rather than “reinventing the wheel.” Source Run

The showMessageDialog Method
JOptionPane.showMessageDialog(null, "Welcome to Java!", "Example 1.2", JOptionPane.INFORMATION_MESSAGE));

The exit Method Use Exit to terminate the program and stop all threads. NOTE: When your program starts, a thread is spawned to run the program. When the showMessageDialog is invoked, a separate thread is spawned to run this method. The thread is not terminated even you close the dialog box. To terminate the thread, you have to invoke the exit method.

Chapter 2 Primitive Data Types and Operations
Introduce Programming with an Example Identifiers, Variables, and Constants Primitive Data Types byte, short, int, long, float, double, char, boolean Expressions Operators, Precedence, Associativity, Operand Evaluation Order: ++, --, *, /, %, +=, -=, *=, /=, %=, ^, &, |, +, -, Getting Input from Input Dialog Boxes Case Studies (Computing Mortgage, and Computing Changes) Style and Documentation Guidelines Syntax Errors, Runtime Errors, and Logic Errors

Introducing Programming with an Example
Example 2.1 Computing the Area of a Circle This program computes the area of the circle. ComputeArea Run

Identifiers An identifier is a sequence of characters that consist of letters, digits, underscores (_), and dollar signs ($). An identifier must start with a letter, an underscore (_), or a dollar sign ($). It cannot start with a digit. An identifier cannot be a reserved word. (See Appendix A, “Java Keywords,” for a list of reserved words). An identifier cannot be true, false, or null. An identifier can be of any length.

Variables // Compute the first area radius = 1.0;
area = radius*radius* ; System.out.println("The area is “ + area + " for radius "+radius); // Compute the second area radius = 2.0;

Declaring Variables int x; // Declare x to be an // integer variable;
double radius; // Declare radius to // be a double variable; char a; // Declare a to be a // character variable;

Assignment Statements
x = 1; // Assign 1 to x; radius = 1.0; // Assign 1.0 to radius; a = 'A'; // Assign 'A' to a;

Declaring and Initializing in One Step
int x = 1; double d = 1.4; float f = 1.4; Is this statement correct?

Constants final datatype CONSTANTNAME = VALUE;
final double PI = ; final int SIZE = 3;

Numerical Data Types byte 8 bits short 16 bits int 32 bits
long bits float bits double bits

Operators +, -, *, /, and % 5/2 yields an integer 2.
5.0/2 yields a double value 2.5 5 % 2 yields 1 (the remainder of the division)

NOTE Calculations involving floating-point numbers are approximated because these numbers are not stored with complete accuracy. For example, System.out.println( ); displays , not 0.5, and System.out.println( ); displays , not 0.1. Integers are stored precisely. Therefore, calculations with integers yield a precise integer result.

Number Literals A literal is a constant value that appears directly in the program. For example, 34, 1,000,000, and 5.0 are literals in the following statements: int i = 34; long l = ; double d = 5.0;

Integer Literals An integer literal can be assigned to an integer variable as long as it can fit into the variable. A compilation error would occur if the literal were too large for the variable to hold. For example, the statement byte b = 1000 would cause a compilation error, because 1000 cannot be stored in a variable of the byte type. An integer literal is assumed to be of the int type, whose value is between -231 ( ) to 231–1 ( ). To denote an integer literal of the long type, append it with the letter L or l. L is preferred because l (lowercase L) can easily be confused with 1 (the digit one).

Floating-Point Literals
Floating-point literals are written with a decimal point. By default, a floating-point literal is treated as a double type value. For example, 5.0 is considered a double value, not a float value. You can make a number a float by appending the letter f or F, and make a number a double by appending the letter d or D. For example, you can use 100.2f or 100.2F for a float number, and 100.2d or 100.2D for a double number.

Scientific Notation Floating-point literals can also be specified in scientific notation, for example, e+2, same as e2, is equivalent to , and e-2 is equivalent to E (or e) represents an exponent and it can be either in lowercase or uppercase.

Arithmetic Expressions
is translated to (3+4*x)/5 – 10*(y-5)*(a+b+c)/x + 9*(4/x + (9+x)/y)

Shortcut Assignment Operators
Operator Example Equivalent += i+=8 i = i+8 -= f-=8.0 f = f-8.0 *= i*=8 i = i*8 /= i/=8 i = i/8 %= i%=8 i = i%8

Increment and Decrement Operators

Increment and Decrement Operators, cont.

Increment and Decrement Operators, cont.
Using increment and decrement operators makes expressions short, but it also makes them complex and difficult to read. Avoid using these operators in expressions that modify multiple variables, or the same variable for multiple times such as this: int k = ++i + i.

Assignment Expressions and Assignment Statements
Prior to Java 2, all the expressions can be used as statements. Since Java 2, only the following types of expressions can be statements: variable op= expression; // Where op is +, -, *, /, or % ++variable; variable++; --variable; variable--;

Numeric Type Conversion
Consider the following statements: byte i = 100; long k = i*3+4; double d = i*3.1+k/2; int x = k; //(Wrong) long k = x; //(fine,implicit casting)

Type Casting double float long int short byte

Type Casting, cont. Implicit casting double d = 3; (type widening)
Explicit casting int i = (int)3.0; (type narrowing) What is wrong? int x = 5/2.0;

Character Data Type char letter = 'A'; (ASCII)
char numChar = '4'; (ASCII) char letter = '\u0041'; (Unicode) char numChar = '\u0034'; (Unicode) Special characters char tab = ‘\t’;

Unicode Format Description Escape Sequence Unicode Backspace \b \u0008
Tab \t \u0009 Linefeed \n \u000a Carriage return \r \u000d

Appendix B: ASCII Character Set
ASCII Character Set is a subset of the Unicode from \u0000 to \u007f

ASCII Character Set, cont.
ASCII Character Set is a subset of the Unicode from \u0000 to \u007f

Casting between char and Numeric Types
int i = 'a'; // Same as int i = (int)'a'; char c = 97; // Same as char c = (char)97;

The boolean Type and Operators
boolean lightsOn = true; boolean lightsOn = false; boolean b = (1 > 2); && (and) (1 < x) && (x < 100) || (or) (lightsOn) || (isDayTime) ! (not) !(isStopped)

Comparison Operators Operator Name < less than
<= less than or equal to > greater than >= greater than or equal to == equal to != not equal to

Boolean Operators Operator Name ! not && and || or ^ exclusive or

Truth Table for Operator !
Operand !Operand true false false true

Truth Table for Operator &&
Operand1 Operand2 Operand1 && Operand2 false false false false true false true false false true true true

Truth Table for Operator ||
Operand1 Operand2 Operand1 || Operand2 false false false false true true true false true true true true

Truth Table for Operator ^
Operand1 Operand2 Operand1 ^ Operand2 false false false false true true true false true true true false

The & and | Operators &&: conditional AND operator
&: unconditional AND operator ||: conditional OR operator |: unconditional OR operator exp1 && exp2 (1 < x) && (x < 100) (1 < x) & (x < 100)

The & and | Operators If x is 1, what is x after this expression?
(x > 1) & (x++ < 10) (1 > x) && ( 1 > x++) How about (1 == x) | (10 > x++)? (1 == x) || (10 > x++)?

Operator Precedence How to evaluate 3 + 4 * 4 > 5 * (4 + 3) - ++i

Operator Precedence var++, var--
+, - (Unary plus and minus), ++var,--var (type) Casting ! (Not) *, /, % (Multiplication, division, and modulus) +, - (Binary addition and subtraction) <, <=, >, >= (Comparison) ==, !=; (Equality) & (Unconditional AND) ^ (Exclusive OR) | (Unconditional OR) && (Conditional AND) Short-circuit AND || (Conditional OR) Short-circuit OR =, +=, -=, *=, /=, %= (Assignment operator)

Operator Associativity
When two operators with the same precedence are evaluated, the associativity of the operators determines the order of evaluation. All binary operators except assignment operators are left-associative. a – b + c – d is equivalent to ((a – b) + c) – d Assignment operators are right-associative. Therefore, the expression a = b += c = 5 is equivalent to a = (b += (c = 5))

Operand Evaluation Order
The precedence and associativity rules specify the order of the operators, but do not specify the order in which the operands of a binary operator are evaluated. Operands are evaluated from left to right in Java. The left-hand operand of a binary operator is evaluated before any part of the right-hand operand is evaluated.

Operand Evaluation Order, cont.
If no operands have side effects that change the value of a variable, the order of operand evaluation is irrelevant. Interesting cases arise when operands do have a side effect. For example, x becomes 1 in the following code, because a is evaluated to 0 before ++a is evaluated to 1. int a = 0; int x = a + (++a); But x becomes 2 in the following code, because ++a is evaluated to 1, then a is evaluated to 1. int x = ++a + a;

Getting Input from Input Dialog Boxes
String string = JOptionPane.showInputDialog( null, “Prompt Message”, “Dialog Title”, JOptionPane.QUESTION_MESSAGE)); where x is a string for the prompting message and y is a string for the title of the input dialog box.

Convertting Strings to Integers
The input returned from the input dialog box is a string. If you enter a numeric value such as 123, it returns “123”. To obtain the input as a number, you have to convert a string into a number. To convert a string into an int value, you can use the static parseInt method in the Integer class as follows: int intValue = Integer.parseInt(intString); where intString is a numeric string such as “123”.

Convertting Strings to Doubles
To convert a string into a double value, you can use the static parseDouble method in the Double class as follows: double doubleValue =Double.parseDouble(doubleString); where doubleString is a numeric string such as “123.45”.

Example 2.2 Entering Input from Dialog Boxes
This program first prompts the user to enter a year as an int value and checks if it is a leap year, it then prompts you to enter a double value and checks if it is positive. A year is a leap year if it is divisible by 4 but not by 100, or it is divisible by 400. InputDialogDemo Run

Example 2.3 Computing Mortgages
This program lets the user enter the interest rate, number of years, and loan amount and computes monthly payment and total payment. ComputeMortgage Run

Example 2.4 Computing Changes
This program lets the user enter the amount in decimal representing dollars and cents and output a report listing the monetary equivalent in single dollars, quarters, dimes, nickels, and pennies. Your program should report maximum number of dollars, then the maximum number of quarters, and so on, in this order. ComputeChange Run

Programming Style and Documentation
Appropriate Comments Naming Conventions Proper Indentation and Spacing Lines Block Styles

Appropriate Comments Include a summary at the beginning of the program to explain what the program does, its key features, its supporting data structures, and any unique techniques it uses. Include your name, class section, instruction, date, and a brief description at the beginning of the program.

Naming Conventions Choose meaningful and descriptive names.
Variables and method names: Use lowercase. If the name consists of several words, concatenate all in one, use lowercase for the first word, and capitalize the first letter of each subsequent word in the name. For example, the variables radius and area, and the method computeArea.

Naming Conventions, cont.
Class names: Capitalize the first letter of each word in the name. For example, the class name ComputeArea. Constants: Capitalize all letters in constants. For example, the constant PI.

Proper Indentation and Spacing
Indent two spaces. Spacing Use blank line to separate segments of the code.

Block Styles Use end-of-line style for braces.

Programming Errors Syntax Errors Runtime Errors Logic Errors
Detected by the compiler Runtime Errors Causes the program to abort Logic Errors Produces incorrect result

Compilation Errors public class ShowSyntaxErrors {
public static void main(String[] args) { i = 30; System.out.println(i+4); }

Runtime Errors public class ShowRuntimeErrors {
public static void main(String[] args) { int i = 1 / 0; }

Logic Errors public class ShowLogicErrors {
// Determine if a number is between 1 and 100 inclusively public static void main(String[] args) { // Prompt the user to enter a number String input = JOptionPane.showInputDialog(null, "Please enter an integer:", "ShowLogicErrors", JOptionPane.QUESTION_MESSAGE); int number = Integer.parseInt(input); // Display the result System.out.println("The number is between 1 and 100, " + "inclusively? " + ((1 < number) && (number < 100))); System.exit(0); }

Chapter 3 Control Statements
Selection Statements Using if and if...else Nested if Statements Using switch Statements Conditional Operator Repetition Statements Looping: while, do-while, and for Nested loops Using break and continue

Selection Statements if Statements switch Statements
Conditional Operators

if Statements Example: if (booleanExpression) { statement(s); }
if ((i > 0) && (i < 10)) { System.out.println("i is an " + "integer between 0 and 10");

Caution Adding a semicolon at the end of an if clause is a common mistake. if (radius >= 0); { area = radius*radius*PI; System.out.println( "The area for the circle of radius " + radius + " is " + area); } This mistake is hard to find, because it is not a compilation error or a runtime error, it is a logic error. This error often occurs when you use the next-line block style. Wrong

The if...else Statement if (booleanExpression) {
statement(s)-for-the-true-case; } else { statement(s)-for-the-false-case;

if...else Example if (radius >= 0) { area = radius*radius*PI;
System.out.println("The area for the “ + “circle of radius " + radius + " is " + area); } else { System.out.println("Negative input");

Multiple Alternative if Statements
if (score >= 90) grade = ‘A’; else if (score >= 80) grade = ‘B’; if (score >= 70) grade = ‘C’; if (score >= 60) grade = ‘D’; grade = ‘F’; if (score >= 90) grade = ‘A’; else if (score >= 80) grade = ‘B’; else if (score >= 70) grade = ‘C’; else if (score >= 60) grade = ‘D’; else grade = ‘F’;

Note The else clause matches the most recent if clause in the same block. For example, the following statement int i = 1; int j = 2; int k = 3; if (i > j) if (i > k) System.out.println("A"); else System.out.println("B"); is equivalent to

Note, cont. Nothing is printed from the preceding statement. To force the else clause to match the first if clause, you must add a pair of braces: int i = 1; int j = 2; int k = 3; if (i > j) { if (i > k) System.out.println("A"); } else System.out.println("B"); This statement prints B.

Nested if Statements Example 3.1 Using Nested if Statements
This program reads in number of years and loan amount and computes the monthly payment and total payment. The interest rate is determined by number of years. TestIfElse

switch Statements switch (year) { case 7: annualInterestRate = 7.25;
break; case 15: annualInterestRate = 8.50; case 30: annualInterestRate = 9.0; default: System.out.println( "Wrong number of years, enter 7, 15, or 30"); }

switch Statement Flow Chart

switch Statement Rules
The switch-expression must yield a value of char, byte, short, or int type and must always be enclosed in parentheses. The value1, ..., and valueN must have the same data type as the value of the switch-expression. The resulting statements in the case statement are executed when the value in the case statement matches the value of the switch-expression. (The case statements are executed in sequential order.) The keyword break is optional, but it should be used at the end of each case in order to terminate the remainder of the switch statement. If the break statement is not present, the next case statement will be executed.

switch Statement Rules, cont.
The default case, which is optional, can be used to perform actions when none of the specified cases is true. · The order of the cases (including the default case) does not matter. However, it is a good programming style to follow the logical sequence of the cases and place the default case at the end.

Caution Do not forget to use a break statement when one is needed. For example, the following code always displays Wrong number of years regardless of what numOfYears is. Suppose the numOfYears is 15. The statement annualInterestRate = 8.50 is executed, then the statement annualInterestRate = 9.0, and finally the statement System.out.println("Wrong number of years"). switch (numOfYears) { case 7: annualInterestRate = 7.25; case 15: annualInterestRate = 8.50; case 30: annualInterestRate = 9.0; default: System.out.println("Wrong number of years"); }

Conditional Operator if (x > 0) y = 1 else y = -1; is equivalent to
y = (x > 0) ? 1 : -1; Ternary operator Binary operator Unary operator

Conditional Operator if (num % 2 == 0)
System.out.println(num + “is even”); else System.out.println(num + “is odd”); System.out.println( (num % 2 == 0)? num + “is even” : num + “is odd”);

Conditional Operator, cont.
(booleanExp) ? exp1 : exp2

Repetitions while Loops do-while Loops for Loops break and continue

while Loop Flow Chart while (continuation-condition) { // loop-body; }

while Loop Flow Chart, cont.
int i = 0; while (i < 100) { System.out.println( "Welcome to Java!"); i++; }

Example 3.2: Using while Loops
TestWhile.java TestWhile

Caution Don’t use floating-point values for equality checking in a loop control. Since floating-point values are approximations, using them could result in imprecise counter values and inaccurate results. This example uses int value for data. If a floating-point type value is used for data, (data != 0) may be true even though data is 0. // data should be zero double data = Math.pow(Math.sqrt(2), 2) - 2; if (data == 0) System.out.println("data is zero"); else System.out.println("data is not zero");

do-while Loop do { // Loop body; } while (continue-condition);

for Loops for (initial-action; loop-continuation-condition; action-after-each-iteration) { //loop body; } int i = 0; while (i < 100) { System.out.println("Welcome to Java! ” + i); i++; Example: int i; for (i = 0; i < 100; i++) {

for Loop Flow Chart for (initial-action; loop-continuation-condition;
action-after-each-iteration) { //loop body; }

for Loop Example int i; for (i = 0; i<100; i++) {
System.out.println( "Welcome to Java"); }

for Loop Examples Examples for using the for loop:
Example 3.3: Using for Loops TestSum Example 3.4: Using Nested for Loops TestMulTable

Which Loop to Use? The three forms of loop statements, while, do, and for, are expressively equivalent; that is, you can write a loop in any of these three forms. I recommend that you use the one that is most intuitive and comfortable for you. In general, a for loop may be used if the number of repetitions is known, as, for example, when you need to print a message 100 times. A while loop may be used if the number of repetitions is not known, as in the case of reading the numbers until the input is 0. A do-while loop can be used to replace a while loop if the loop body has to be executed before testing the continuation condition.

Caution Adding a semicolon at the end of the for clause before the loop body is a common mistake, as shown below: for (int i=0; i<10; i++); { System.out.println("i is " + i); } Wrong

Caution, cont. Similarly, the following loop is also wrong:
int i=0; while (i<10); { System.out.println("i is " + i); i++; } In the case of the do loop, the following semicolon is needed to end the loop. do { } while (i<10); Wrong Correct

The break Keyword

The continue Keyword

Using break and continue
Examples for using the break and continue keywords: Example 3.5: TestBreak.java TestBreak Example 3.6: TestContinue.java TestContinue

Example 3.7 Finding the Sales Amount
You have just started a sales job in a department store. Your pay consists of a base salary and a commission. The base salary is $5,000. The scheme shown below is used to determine the commission rate. Sales Amount Commission Rate $0.01–$5, percent $5,000.01–$10, percent $10, and above 12 percent Your goal is to earn $30,000 in a year. Write a program that will find out the minimum amount of sales you have to generate in order to make $30,000. FindSalesAmount Run

Example 3.8 Displaying a Pyramid of Numbers
In this example, you will use nested loops to print the following output: 1 212 32123 Your program prints five lines. Each line consists of three parts. The first part comprises the spaces before the numbers; the second part, the leading numbers, such as on line 3; and the last part, the ending numbers, such as 2 3 on line 3. PrintPyramid Run

Example 3.9 Displaying Prime Numbers
This example displays the first 50 prime numbers in five lines, each of which contains 10 numbers. An integer greater than 1 is prime if its only positive divisor is 1 or itself. For example, 2, 3, 5, and 7 are prime numbers, but 4, 6, 8, and 9 are not. The problem can be broken into the following tasks: For number = 2, 3, 4, 5, 6, ..., test whether the number is prime. Determine whether a given number is prime. Count the prime numbers. Print each prime number, and print 10 numbers per line. PrimeNumber Run

Chapter 4 Methods Introducing Methods Passing Parameters
Benefits of methods, Declaring Methods, and Calling Methods Passing Parameters Pass by Value Overloading Methods Ambiguous Invocation Scope of Local Variables Method Abstraction The Math Class Case Studies Recursion (Optional)

Introducing Methods Method Structure A method is a collection of statements that are grouped together to perform an operation.

Introducing Methods, cont.
parameter profile refers to the type, order, and number of the parameters of a method. method signature is the combination of the method name and the parameter profiles. The parameters defined in the method header are known as formal parameters. When a method is invoked, its formal parameters are replaced by variables or data, which are referred to as actual parameters.

Declaring Methods public static int max(int num1, int num2) {
if (num1 > num2) return num1; else return num2; }

Calling Methods Example 4.1 Testing the max method
This program demonstrates calling a method max to return the largest of the int values TestMax

Calling Methods, cont.

CAUTION A return statement is required for a nonvoid method. The following method is logically correct, but it has a compilation error, because the Java compiler thinks it possible that this method does not return any value. public static int xMethod(int n) { if (n > 0) return 1; else if (n == 0) return 0; else if (n < 0) return –1; } To fix this problem, delete if (n<0) in the code.

Passing Parameters public static void nPrintln(String message, int n) { for (int i = 0; i < n; i++) System.out.println(message); }

Pass by Value Example 4.2 Testing Pass by value
This program demonstrates passing values to the methods. TestPassByValue

Pass by Value, cont.

TestMethodOverloading
Overloading Methods Example 4.3 Overloading the max Method public static double max(double num1, double num2) { if (num1 > num2) return num1; else return num2; } TestMethodOverloading

Ambiguous Invocation Sometimes there may be two or more possible matches for an invocation of a method, but the compiler cannot determine the most specific match. This is referred to as ambiguous invocation. Ambiguous invocation is a compilation error.

Ambiguous Invocation public class AmbiguousOverloading {
public static void main(String[] args) { System.out.println(max(1, 2)); } public static double max(int num1, double num2) { if (num1 > num2) return num1; else return num2; public static double max(double num1, int num2) {

Scope of Local Variables
A local variable: a variable defined inside a method. Scope: the part of the program where the variable can be referenced. The scope of a local variable starts from its declaration and continues to the end of the block that contains the variable. A local variable must be declared before it can be used.

Scope of Local Variables, cont.
You can declare a local variable with the same name multiple times in different non-nesting blocks in a method, but you cannot declare a local variable twice in nested blocks. Thus, the following code is correct.

// Fine with no errors public static void correctMethod() { int x = 1; int y = 1; // i is declared for (int i = 1; i < 10; i++) { x += i; } // i is declared again y += i;

// With no errors public static void incorrectMethod() { int x = 1; int y = 1; for (int i = 1; i < 10; i++) { int x = 0; x += i; }

Method Abstraction You can think of the method body as a black box that contains the detailed implementation for the method.

Benefits of Methods Write once and reuse it any times.
Information hiding. Hide the implementation from the user. Reduce complexity.

The Math Class Class constants: Class methods: PI E
Trigonometric Methods Exponent Methods Rounding Methods min, max, abs, and random Methods

Trigonometric Methods
sin(double a) cos(double a) tan(double a) acos(double a) asin(double a) atan(double a)

Exponent Methods exp(double a) Returns e raised to the power of a.
log(double a) Returns the natural logarithm of a. pow(double a, double b) Returns a raised to the power of b. sqrt(double a) Returns the square root of a.

Rounding Methods double ceil(double x)
x rounded up to its nearest integer. This integer is returned as a double value. double floor(double x) x is rounded down to its nearest integer. This integer is returned as a double value. double rint(double x) x is rounded to its nearest integer. If x is equally close to two integers, the even one is returned as a double. int round(float x) Return (int)Math.floor(x+0.5). long round(double x) Return (long)Math.floor(x+0.5).

min, max, abs, and random max(a, b)and min(a, b) abs(a) random()
Returns the maximum or minimum of two parameters. abs(a) Returns the absolute value of the parameter. random() Returns a random double value in the range [0.0, 1.0).

Example 4.4 Computing Mean and Standard Deviation
Generate 10 random numbers and compute the mean and standard deviation ComputeMeanDeviation

Example 4.5 Obtaining Random Characters
Write the methods for generating random characters. The program uses these methods to generate 175 random characters between ‘!' and ‘~' and displays 25 characters per line. To find out the characters between ‘!' and ‘~', see Appendix B, “The ASCII Character Set.” RandomCharacter

Example 4.5 Obtaining Random Characters, cont.
Appendix B: ASCII Character Set

Case Studies Example 4.6 Displaying Calendars
The program reads in the month and year and displays the calendar for a given month of the year. PrintCalendar

Design Diagram

Recursion (Optional) Example 4.7 Computing Factorial factorial(0) = 1;
factorial(n) = n*factorial(n-1); ComputeFactorial

Example 4.7 Computing Factorial, cont.

Fibonacci Numbers Example 4.8 Computing Finonacci Numbers
… f0 f1 fib(2) = fib(0) + fib(1); fib(0) = 0; fib(1) = 1; fib(n) = fib(n-2) + fib(n-1); n>=2

Fibonacci Numbers, cont
ComputeFibonacci

Fibonnaci Numbers, cont.

Towers of Hanoi Example 4.9 Solving the Towers of Hanoi Problem
Solve the towers of Hanoi problem. TowersOfHanoi

Towers of Hanoi, cont.

Chapter 5 Arrays Introducing Arrays
Declaring Array Variables, Creating Arrays, and Initializing Arrays Passing Arrays to Methods Copying Arrays Multidimensional Arrays Search and Sorting Methods

Introducing Arrays Array is a data structure that represents a collection of the same types of data. An Array of 10 Elements of type double

Declaring Array Variables
datatype[] arrayname; Example: double[] myList; datatype arrayname[]; double myList[];

Creating Arrays arrayName = new datatype[arraySize]; Example:
myList = new double[10]; myList[0] references the first element in the array. myList[9] references the last element in the array.

Declaring and Creating in One Step
datatype[] arrayname = new datatype[arraySize]; double[] myList = new double[10]; datatype arrayname[] = new datatype[arraySize]; double myList[] = new double[10];

The Length of Arrays arrayVariable.length For example,
Once an array is created, its size is fixed. It cannot be changed. You can find its size using arrayVariable.length For example, myList.length returns 10

Initializing Arrays This shorthand syntax must be in one statement.
Using a loop: for (int i = 0; i < myList.length; i++) myList[i] = i; Declaring, creating, initializing in one step: double[] myList = {1.9, 2.9, 3.4, 3.5}; This shorthand syntax must be in one statement.

Declaring, creating, initializing Using the Shorthand Notation
double[] myList = {1.9, 2.9, 3.4, 3.5}; This shorthand notation is equivalent to the following statements: double[] myList = new double[4]; myList[0] = 1.9; myList[1] = 2.9; myList[2] = 3.4; myList[3] = 3.5;

CAUTION Using the shorthand notation, you have to declare, create, and initialize the array all in one statement. Splitting it would cause a syntax error. For example, the following is wrong: double[] myList; myList = {1.9, 2.9, 3.4, 3.5};

Example 5.1 Testing Arrays
Objective: The program receives 6 numbers from the keyboard, finds the largest number and counts the occurrence of the largest number entered from the keyboard. Suppose you entered 3, 5, 2, 5, 5, and 5, the largest number is 5 and its occurrence count is 4. TestArray Run

Example 5.2 Assigning Grades
Objective: read student scores (int) from the keyboard, get the best score, and then assign grades based on the following scheme: Grade is A if score is >= best–10; Grade is B if score is >= best–20; Grade is C if score is >= best–30; Grade is D if score is >= best–40; Grade is F otherwise. AssignGrade Run

Passing Arrays to Methods
Java uses pass by value to pass parameters to a method. There are important differences between passing a value of variables of primitive data types and passing arrays. For a parameter of a primitive type value, the actual value is passed. Changing the value of the local parameter inside the method does not affect the value of the variable outside the method. For a parameter of an array type, the value of the parameter contains a reference to an array; this reference is passed to the method. Any changes to the array that occur inside the method body will affect the original array that was passed as the argument.

Example 5.3 Passing Arrays as Arguments
Objective: Demonstrate differences of passing primitive data type variables and array variables. TestPassArray Run

Example 5.3, cont.

Example 5.4 Computing Deviation Using Arrays
Run

Example 5.5 Counting Occurrence of Each Letter
Generate 100 lowercase letters randomly and assign to an array of characters. Count the occurrence of each letter in the array. Find the mean and standard deviation of the counts. CountLettersInArray Run

Example 5.6 Copying Arrays
In this example, you will see that a simple assignment cannot copy arrays in the following program. The program simply creates two arrays and attempts to copy one to the other, using an assignment statement. TestCopyArray Run

Copying Arrays

Copying Arrays Using a loop: int[] sourceArray = {2, 3, 1, 5, 10};
int[] targetArray = new int[sourceArray.length]; for (int i = 0; i < sourceArrays.length; i++) targetArray[i] = sourceArray[i];

The arraycopy Utility arraycopy(sourceArray, src_pos, targetArray, tar_pos, length); Example: System.arraycopy(sourceArray, 0, targetArray, 0, sourceArray.length);

Multidimensional Arrays
Declaring Variables of Multidimensional Arrays and Creating Multidimensional Arrays int[][] matrix = new int[10][10]; or int matrix[][] = new int[10][10]; matrix[0][0] = 3; for (int i=0; i<matrix.length; i++) for (int j=0; j<matrix[i].length; j++) { matrix[i][j] = (int)(Math.random()*1000); } double[][] x;

Multidimensional Array Illustration

Declaring, Creating, and Initializing Using Shorthand Notations
You can also use a shorthand notation to declare, create and initialize a two-dimensional array. For example, int[][] array = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9}, {10, 11, 12} }; This is equivalent to the following statements: int[][] array = new int[4][3]; array[0][0] = 1; array[0][1] = 2; array[0][2] = 3; array[1][0] = 4; array[1][1] = 5; array[1][2] = 6; array[2][0] = 7; array[2][1] = 8; array[2][2] = 9; array[3][0] = 10; array[3][1] = 11; array[3][2] = 12;

Lengths of Multidimensional Arrays
int[][] array = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9}, {10, 11, 12} }; array.length array[0].length array[1].length array[2].length

Ragged Arrays Each row in a two-dimensional array is itself an array. So, the rows can have different lengths. Such an array is known as a ragged array. For example, int[][] matrix = { {1, 2, 3, 4, 5}, {2, 3, 4, 5}, {3, 4, 5}, {4, 5}, {5} };

Example 5.7 Adding and Multiplying Two Matrices
Objective: Use two-dimensional arrays to create two matrices, and then add and multiply the two matrices. TestMatrixOperation Run

Example 5.7 (cont) Adding and Multiplying Two Matrices
cij = ai1b1j+ai2b2j+ai3b3j+ai4b4j+ai5b5j

Example 5.8 Grading Multiple-Choice Test
Objective: write a program that grades multiple-choice test. Grade Exam Run

Example 5.9 Calculating Total Scores
Objective: write a program that calculates the total score for students in a class. Suppose the scores are stored in a three-dimensional array named scores. The first index in scores refers to a student, the second refers to an exam, and the third refers to the part of the exam. Suppose there are 7 students, 5 exams, and each exam has two parts--the multiple-choice part and the programming part. So, scores[i][j][0] represents the score on the multiple-choice part for the i’s student on the j’s exam. Your program displays the total score for each student, . Run TotalScore

Searching Arrays Searching is the process of looking for a specific element in an array; for example, discovering whether a certain score is included in a list of scores. Searching, like sorting, is a common task in computer programming. There are many algorithms and data structures devoted to searching. In this section, two commonly used approaches are discussed, linear search and binary search.

Linear Search The linear search approach compares the key element, key, with each element in the array list[]. The method continues to do so until the key matches an element in the list or the list is exhausted without a match being found. If a match is made, the linear search returns the index of the element in the array that matches the key. If no match is found, the search returns -1.

Example 5.10 Testing Linear Search
Objective: Implement and test the linear search method by creating an array of 10 elements of int type randomly and then display this array. Prompt the user to enter a key for testing the linear search. LinearSearch Run

Binary Search For binary search to work, the elements in the array must already be ordered. Without loss of generality, assume that the array is in ascending order. e.g The binary search first compares the key with the element in the middle of the array. Consider the following three cases:

Binary Search, cont. · If the key is less than the middle element, you only need to search the key in the first half of the array. · If the key is equal to the middle element, the search ends with a match. · If the key is greater than the middle element, you only need to search the key in the second half of the array.

Binary Search, cont.

Example 5.11 Testing Binary Search
Objective: Implement and test the binary search method. The program first creates an array of 10 elements of int type. It displays this array and then prompts the user to enter a key for testing binary search. BinarySearch Run

Example 5.12 Using Arrays in Sorting
Objective: Use the selectionSort method to write a program that will sort a list of double floating-point numbers. int[] myList = {2, 9, 5, 4, 8, 1, 6}; // Unsorted Sort it to produce 1, 2, 4, 5, 6, 8, 9 2, 9, 5, 4, 8, 1, 6 SelectionSort Run

Example 5.12: (Cont) Using Arrays in Sorting
int[] myList = {2, 9, 5, 4, 8, 1, 6}; // Unsorted Find the largest element in myList and swap it with the last element in myList. 2, 9, 5, 4, 8, 1, 6 => 2, 6, 5, 4, 8, 1, 9 (size = 7) 2, 6, 5, 4, 8, 1 => 2, 6, 5, 4, 1, 8 (size = 6) 2, 6, 5, 4, 1 => 2, 1, 5, 4, 6 (size = 5) 2, 1, 5, 4 => 2, 1, 4, 5 2, 1, 4 => 2, 1, 4, 2, 1 => 1, 2 Sort it to produce 1, 2, 4, 5, 6, 8, 9

Exercise 5.5: Bubble Sort int[] myList = {2, 9, 5, 4, 8, 1, 6}; // Unsorted Pass 1: 2, 5, 4, 8, 1, 6, 9 Pass 2: 2, 4, 5, 1, 6, 8, 9 Pass 3: 2, 4, 1, 5, 6, 8, 9 Pass 4: 2, 1, 4, 5, 6, 8, 9 Pass 5: 1, 2, 4, 5, 6, 8, 9 Pass 6: 1, 2, 4, 5, 6, 8, 9

Chapter 6 Objects and Classes
OO Programming Concepts Creating Objects and Object Reference Variables Differences between primitive data type and object type Automatic garbage collection Constructors Modifiers (public, private and static) Instance and Class Variables and Methods Scope of Variables Use the this Keyword Case Studies (Mortgage class and Count class)

OO Programming Concepts

Class and Objects

Class Declaration class Circle { double radius = 1.0;
double findArea(){ return radius * radius * ; }

Declaring Object Reference Variables
ClassName objectReference; Example: Circle myCircle;

Creating Objects Example:
objectReference = new ClassName(); Example: myCircle = new Circle(); The object reference is assigned to the object reference variable.

Declaring/Creating Objects in a Single Step
ClassName objectReference = new ClassName(); Example: Circle myCircle = new Circle();

Differences between variables of primitive Data types and object types

Copying Variables of Primitive Data Types and Object Types

Garbage Collection As shown in the previous figure, after the assignment statement c1 = c2, c1 points to the same object referenced by c2. The object previously referenced by c1 is no longer useful. This object is known as garbage. Garbage is automatically collected by JVM.

Garbage Collection, cont
TIP: If you know that an object is no longer needed, you can explicitly assign null to a reference variable for the object. The Java VM will automatically collect the space if the object is not referenced by any variable.

Accessing Objects Referencing the object’s data: objectReference.data
myCircle.radius Invoking the object’s method: objectReference.method myCircle.findArea()

Example 6.1 Using Objects Objective: Demonstrate creating objects, accessing data, and using methods. TestCircle Run

Constructors Circle(double r) { radius = r; }
myCircle = new Circle(5.0); Constructors are a special kind of methods that are invoked to construct objects.

Constructors, cont. A constructor with no parameters is referred to as a default constructor. · Constructors must have the same name as the class itself. · Constructors do not have a return type—not even void. · Constructors are invoked using the new operator when an object is created. Constructors play the role of initializing objects.

Example 6.2 Using Classes from the Java Library
Objective: Demonstrate using classes from the Java library. Use the JFrame class in the javax.swing package to create two frames; use the methods in the JFrame class to set the title, size and location of the frames and to display the frames. TestFrame Run

Example 6.3 Using Constructors
Objective: Demonstrate the role of constructors and use them to create objects. TestCircleWithConstructors Run

Visibility Modifiers and Accessor Methods
By default, the class, variable, or data can be accessed by any class in the same package. public The class, data, or method is visible to any class in any package. private The data or methods can be accessed only by the declaring class. The get and set methods are used to read and modify private properties.

Example 6.4 Using the private Modifier and Accessor Methods
In this example, private data are used for the radius and the accessor methods getRadius and setRadius are provided for the clients to retrieve and modify the radius. TestCircleWithAccessors Run

Passing Objects to Methods
Passing by value (the value is the reference to the object) Example 6.5 Passing Objects as Arguments TestPassingObject Run

Passing Objects to Methods, cont.

Instance Variables, and Methods
Instance variables belong to a specific instance. Instance methods are invoked by an instance of the class.

Class Variables, Constants, and Methods
Class variables are shared by all the instances of the class. Class methods are not tied to a specific object. Class constants are final variables shared by all the instances of the class.

Class Variables, Constants, and Methods, cont.
To declare class variables, constants, and methods, use the static modifier.

Class Variables, Constants, and Methods, cont.

Example 6.6 Using Instance and Class Variables and Method
Objective: Demonstrate the roles of instance and class variables and their uses. This example adds a class variable numOfObjects to track the number of Circle objects created. TestCircleWithStaticVariable Run

Scope of Variables The scope of instance and class variables is the entire class. They can be declared anywhere inside a class. The scope of a local variable starts from its declaration and continues to the end of the block that contains the variable. A local variable must be declared before it can be used.

The Keyword this Use this to refer to the current object.
Use this to invoke other constructors of the object.

Array of Objects Circle[] circleArray = new Circle[10]; An array of objects is actually an array of reference variables. So invoking circleArray[1].findArea() involves two levels of referencing as shown in the next figure. circleArray references to the entire array. circleArray[1] references to a Circle object.

Array of Objects, cont. Circle[] circleArray = new Circle[10];

Array of Objects, cont. Example 6.7: Summarizing the areas of the circles TotalArea Run

Class Abstraction Class abstraction means to separate class implementation from the use of the class. The creator of the class provides a description of the class and let the user know how the class can be used. The user of the class does not need to know how the class is implemented. The detail of implementation is encapsulated and hidden from the user.

Example 6.8 The Mortgage Class
TestMortgageClass Run

Example 6.9 The Count Class
Run TestVoteCandidate

Java API and Core Java classes
java.lang Contains core Java classes, such as numeric classes, strings, and objects. This package is implicitly imported to every Java program. java.awt Contains classes for graphics. java.applet Contains classes for supporting applets.

Java API and Core Java classes, cont.
java.io Contains classes for input and output streams and files. java.util Contains many utilities, such as date. java.net Contains classes for supporting network communications.

Java API and Core Java classes, cont.
java.awt.image Contains classes for managing bitmap images. java.awt.peer Platform-specific GUI implementation. Others: java.sql java.rmi

Chapter 7 Strings To process strings using the String class, the StringBuffer class, and the StringTokenizer class. To use the String class to process fixed strings. To use static methods in the Character class. To use the StringBuffer class to process flexible strings. To use the StringTokenizer class to extract tokens from a string. To use the command-line arguments.

The String Class Constructing a String:
String message = "Welcome to Java!" String message = new String("Welcome to Java!“); String s = new String(); Obtaining String length and Retrieving Individual Characters in a string String String Concatenation (concat) Substrings (substring(index), substring(start, end)) Comparisons (equals, compareTo) String Conversions Finding a Character or a Substring in a String Conversions between Strings and Arrays Converting Characters and Numeric Values to Strings

Constructing Strings Strings newString = new String(stringLiteral);
String message = new String("Welcome to Java!"); Since strings are used frequently, Java provides a shorthand notation for creating a string: String message = "Welcome to Java!";

Strings Are Immutable NOTE: A String object is immutable, whose contents cannot be changed. To improve efficiency and save memory, Java Virtual Machine stores two String objects into the same object, if the two String objects are created with the same string literal using the shorthand notation. Therefore, the shorthand notation is preferred to create strings.

Strings Are Immutable, cont.
NOTE: A string that is created using the shorthand notation is known as a canonical string. You can use the String’s intern method to return a canonical string, which is the same string that is created using the shorthand notation.

Examples String s = "Welcome to Java!";
String s1 = new String("Welcome to Java!"); String s2 = s1.intern(); System.out.println("s1 == s is " + (s1 == s)); System.out.println("s2 == s is " + (s2 == s)); System.out.println("s1 == s2 is " + (s1 == s2)); display s1 == s is false s2 == s is true s1 == s2 false

Finding String Length Finding string length using the length() method:
message = "Welcome"; message.length() (returns 7)

Retrieving Individual Characters in a String
Do not use message[0] Use message.charAt(index) Index starts from 0

String Concatenation String s3 = s1.concat(s2); String s3 = s1 + s2;

Extracting Substrings
String is an immutable class; its values cannot be changed individually. String s1 = "Welcome to Java"; String s2 = s1.substring(0, 11) + "HTML";

String Comparisons equals String s1 = "Welcome";
if (s1.equals(s2)){ // s1 and s2 have the same contents } if (s1 == s2) { // s1 and s2 have the same reference

String Comparisons, cont.
compareTo(Object object) String s1 = "Welcome"; String s2 = "welcome"; if (s1.compareTo(s2) > 0) { // s1 is greater than s2 } else if (s1.compareTo(s2 == 0) { // s1 and s2 have the same reference else // s1 is less than s2

String Conversions The contents of a string cannot be changed once the string is created. But you can convert a string to a new string using the following methods: toLowerCase toUpperCase trim replace(oldChar, newChar)

Finding a Character or a Substring in a String
"Welcome to Java!".indexOf('W')) returns 0. "Welcome to Java!".indexOf('x')) returns -1. "Welcome to Java!".indexOf('o', 5)) returns 9. "Welcome to Java!".indexOf("come")) returns 3. "Welcome to Java!".indexOf("Java", 5)) returns 11. "Welcome to Java!".indexOf("java", 5)) returns -1.

Convert Character and Numbers to Strings
The String class provides several static valueOf methods for converting a character, an array of characters, and numeric values to strings. These methods have the same name valueOf with different argument types char, char[], double, long, int, and float. For example, to convert a double value to a string, use String.valueOf(5.44). The return value is string consists of characters ‘5’, ‘.’, ‘4’, and ‘4’.

Example 7.1 Finding Palindromes
Objective: Checking whether a string is a palindrome: a string that reads the same forward and backward. Run CheckPalindrome

The Character Class

Examples charObject.compareTo(new Character('a')) returns 1
charObject.compareTo(new Character('b')) returns 0 charObject.compareTo(new Character('c')) returns -1 charObject.compareTo(new Character('d') returns –2 charObject.equals(new Character('b')) returns true charObject.equals(new Character('d')) returns false

Example 7.2 Counting Each Letter in a String
This example gives a program that counts the number of occurrence of each letter in a string. Assume the letters are not case-sensitive. Run CountEachLetter

The StringBuffer Class
The StringBuffer class is an alternative to the String class. In general, a string buffer can be used wherever a string is used. StringBuffer is more flexible than String. You can add, insert, or append new contents into a string buffer. However, the value of a string is fixed once the string is created.

StringBuffer Constructors
public StringBuffer() No characters, initial capacity 16 characters. public StringBuffer(int length) No characters, initial capacity specified by the length argument. public StringBuffer(String str) Represents the same sequence of characters as the string argument. Initial capacity 16 plus the length of the string argument.

Appending New Contents into a String Buffer
StringBuffer strBuf = new StringBuffer(); strBuf.append("Welcome"); strBuf.append(' '); strBuf.append("to"); strBuf.append("Java");

Example 7.3 Checking Palindromes Ignoring Non-alphanumeric Characters
This example gives a program that counts the number of occurrence of each letter in a string. Assume the letters are not case-sensitive. Run PalindromeIgnoreNonAlphanumeric

Example 7.4 Using StringBuffer for Output
This This example gives a program that prints the multiplication table created in Example 3.4, "Using Nested for Loops," from Chapter 3. Rather than print one number at a time, the program appends all the elements of the table into a string buffer. After the table is completely constructed in the string buffer, the program prints the entire string buffer on the console once. Run TestMulTableUsingStringBuffer

The StringTokenizer Class Constructors
StringTokenizer(String s, String delim, boolean returnTokens) StringTokenizer(String s, String delim) StringTokenizer(String s)

The StringTokenizer Class Methods
boolean hasMoreTokens() String nextToken() String nextToken(String delim)

Example 7.5 Testing StringTokenizer
Objective: Using a string tokenizer, retrieve words from a string and display them on the console. TestStringTokenizer Run

Command-Line Parameters
class TestMain { public static void main(String[] args) { ... } java TestMain arg0 arg1 arg2 ... argn

Processing Command-Line Parameters
In the main method, get the arguments from args[0], args[1], ..., args[n], which corresponds to arg0, arg1, ..., argn in the command line. Example 12.4

Example 7.6 Using Command-Line Parameters
Objective: Write a program that will perform binary operations on integers. The program receives three parameters: an operator and two integers. java Calculator + 2 3 Calculator java Calculator - 2 3 java Calculator / 2 3 Run java Calculator “*” 2 3

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