 # 1 Chapter 2: Elementary Programming Shahriar Hossain.

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1 Chapter 2: Elementary Programming Shahriar Hossain

Quiz solution F What will be the value of the variable x after performing the following Java statement: int x = 7 − 10 % 2 / 3; Solution: 7 2 Consecutive multiplicative operators will be evaluated from left to right in the expression since they have the same priority.

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Quiz solution F What will be printed as a result of the following piece of code? explain step-by- step: double x = 3; double y = x + 1; x = y − 2; System.out.println(x); System.out.println(y); Solution : 2.0 4.0 4

5 Objectives F To use augmented assignment operators F To distinguish between postincrement and preincrement and between postdecrement and predecrement F To cast the value of one type to another type F To represent characters using the char type F To represent a string using the String type F To become familiar with Java programming style and documentation

6 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;

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

8 Numeric Operators

9 Augmented Assignment Operators OperatorExampleEquivalent +=i += 8i = i + 8 -=f -= 8.0f = f - 8.0 *=i *= 8i = i * 8 /=i /= 8i = i / 8 %=i %= 8i = i % 8 The operators +, -, *, /, and % can be combined with the assignment operator to form augmented operators.

Caution F There is no spaces in the augmented assignment operators + = is wrong += is correct 10

11 Increment and Decrement Operators OperatorNameDescription ++varpreincrementThe expression (++var) increments var by 1 and evaluates to the new value in var after the increment. var++postincrementThe expression (var++) evaluates to the original value in var and increments var by 1. --varpredecrementThe expression (--var) decrements var by 1 and evaluates to the new value in var after the decrement. var--postdecrement The expression (var--) evaluates to the original value in var and decrements var by 1.

12 Increment and Decrement Operators, cont.

13 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.

14 Increment and Decrement Operators, cont. What is the output of the following code segment? int i=2; int k=++i+i; System.out.println(i); System.out.println(k); 3636

15 Increment and Decrement Operators, cont. What is the output of the following code segment? int i=2; int k=i+++i; // equivalent to int k=(i++)+i; System.out.println(i); System.out.println(k); 3535

16 Numeric Type Conversion Consider the following statements: byte i = 100; long k = i * 3 + 4; double d = i * 3.1 + k / 2;

17 Conversion Rules When performing a binary operation involving two operands of different types, Java automatically converts the operand based on the following rules: 1. If one of the operands is double, the other is converted into double. 2. Otherwise, if one of the operands is float, the other is converted into float. 3. Otherwise, if one of the operands is long, the other is converted into long. 4. Otherwise, both operands are converted into int.

18 Type Casting Implicit casting double d = 3; (type widening) Explicit casting int i = (int)3.0; (type narrowing) int i = (int)3.9; (Fraction part is truncated) What is wrong? int x = 5 / 2.0; The correct statement is int i=(int)(5/2.0);

19 Type Casting

20 Casting in an Augmented Expression In Java, an augmented expression of the form x1 op= x2 is implemented as x1 = (T)(x1 op x2), where T is the type for x1. Therefore, the following code is correct. int sum = 0; sum += 4.5; // sum becomes 4 after this statement sum += 4.5 is equivalent to sum = (int)(sum + 4.5).

21 Character Data Type char letter = 'A'; (ASCII) char numChar = '4'; (ASCII) char letter = '\u0041'; (Unicode) char numChar = '\u0034'; (Unicode) Four hexadecimal digits. NOTE: The increment and decrement operators can also be used on char variables to get the next or preceding Unicode character. For example, the following statements display character b. char ch = 'a'; System.out.println(++ch);

ASCII (The American Standard Code for Information Interchange) 22

Unicode F An encoding scheme established by the Unicode Consortium F Originally 16-bit but there are supplementary characters beyond the 16-bit limit 23

24 Escape Sequences for Special Characters Description Escape Sequence Unicode Backspace \b\u0008 Tab \t\u0009 Linefeed \n\u000A Carriage return \r\u000D Backslash \\\u005C Single Quote \ ' \u0027 Double Quote \ " \u0022

Example F Is this a correct statement? System.out.println("He said "Java is fun" "); F No. The statement above will give a compiler error F The correct statement will be System.out.println("He said \"Java is fun\" "); 25

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