1. Know for Quiz Everything through Last Week and Lab 7
Loops: while, for, do-while
switch-case Statement

2. Strings Revisited String Is a Type (Object) in JAVA
Automatically imported in java.lang
May Initialize or Assign with Double Quoted Values
Can Add String to String with ‘+’ Operator
CANNOT Compare using Equality Operators (uses .equals() method instead)
Methods Available to
Access single characters
Get length of String
Compare Strings

3. Objects Objects: Types of Variables Made from Built-In Types
Variables Can be Declared as an Object Type
Objects Usually Have Functions Tied to Them
Member functions
Public functions
Interface functions
Methods
String Is an Example of an Object Type
StringVariable.length() Returns the Number of Characters in the String

4. Methods Also called Procedures, Functions
Have Parenthesis (e.g., method() )
May be Passed Arguments, or Parameters
Parameters are values to initialize new variables in method
Parameters used to pass information to method

5. String Methods
charAt(int index): return char at named index (starting at 0)
equals(String str): return boolean
length(): return int length of String

6. String myString = "My Dog Sandy",compareString;
System.out.println("The fourth character is: " + myString.charAt(3));
if (myString.equals("my dog sandy"))
System.out.println("Strings are equal");
else
System.out.println("Strings are not equal");
compareString = myString + myString;
System.out.println("Added strings are: " + compareString);
Output:
The fourth character is: D
Strings are not equal
Added strings are: My Dog SandyMy Dog Sandy

7. System.out.println("Length of string is: " + myString.length());
Output:
Length of string is: 12

8. import java.util.Scanner;
public class MyProgram {
public static void main( String [ ] args)
Scanner scan = new Scanner(System.in);
String lastname;
boolean instructor = false;
System.out.print(“Enter last name:”);
lastname = scan.next();
if(lastname.equals(“hanrath”))
instructor = true; // privileged
else
instructor = false; // not privileged }

9. More on Input Input Failure Common *MUST* Be Part of Test Plan
Pages in Anderson
Check Input for Type Desired
hasNextInt(), hasNextDouble()
If not, Notify User, and Get Rid of Line
Once hasNotXXX() returns true, safe to read in value

10. Input Failure Example import java.util.*; class InputFailureExample {
public static void main(String[] args)
int numE;
String garbage;
Scanner scan = new Scanner(System.in);
System.out.print("Enter Integer: ");
while (!scan.hasNextInt())
garbage = scan.nextLine();
System.out.println("Please try again."); }
numE = scan.nextInt();
System.out.println("You entered: " + numE);

11. Arrays Syntax: type variableName[] = new type [size];
Memory Is Set Aside for size Items of type
Each Variable Location in Array Is Accessed by Offsetting into the Array with an Integer Expression
Legitimate Offsets Are 0 to size-1

12. Array Example int [] values = new int[15]; values[0] = 150;
System.out.println( values[0]);
values[3] = values[0] + 6;

13. Array Example final int ARRAY_SIZE = 100; int offset;
int [] numArray = new int [ARRAY_SIZE];
for(offset = 0; offset < ARRAY_SIZE; offset++) {
numArray[offset] = 0; }
for(offset = 0; offset < numArray.length; offset++)
numArray[offset] = offset;

14. Files Data in Main Memory is “volatile”
File: Place for “permanent” data storage
C: drive, A: drive, Flash drive, etc.
Main Memory
File
main()
int num;
string firstname;
Disk

15. Output File Streams import java.io.*; class FileOutput {
public static void main(String [ ] args) throws IOException
int i;
FileOutputStream ofile = new FileOutputStream("data2.txt",false); //true:APP
PrintWriter pw = new PrintWriter(ofile);
for (i=0;i < 100; i = i + 2)
pw.println(i); }
pw.close(); // Writes data to file on disk

16. Input Files import java.io.*; import java.util.Scanner;
class FileInput {
public static void main(String [ ] args) throws IOException
File ifile = new File("data2.txt");
Scanner scan = new Scanner(ifile);
while (scan.hasNextInt())
i = scan.nextInt(); }

17. mydata.txt file 5 8 9.3 Jon 6 14.335 Bill 0 35.67e9 Mary
import java.util.Scanner;
import java.io.*;
class FormatFileData {
public static void main(String [ ] args) throws IOException
int loops, integer, i;
float decimal;
String name;
File ifile = new File("mydata.txt");
Scanner scan = new Scanner(ifile);
loops = scan.nextInt();
for(i= 0 ; i < loops; i++)
integer = scan.nextInt();
decimal = scan.nextFloat();
name= scan.next();
System.out.print(integer + " ");
System.out.print(decimal + " ");
System.out.print(name + " ");
System.out.println(); }
mydata.txt file 5
8 9.3 Jon
Bill
e9 Mary
Smith
-3 -4e3 xyz
Output:
8 9.3 Jon
Bill
E10 Mary
Smith
-3 – xyz

18. Know for Quiz 2 Everything through Last Week and Lab 7
Loops: while, for, do-while
switch-case Statement