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10/2/2014 Ebtsam AbdelHakam 1
Object Oriented Programming Lecture (2.1)
Supervisor Ebtsam AbdelHakam
ebtsamabd@gmail.com Department of Computer Science
Najran University
Outline
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● Operators Arithmetic Operators. Relational Operators. Boolean Logical Operators Assignment Operator The ? Operator. Operator Precedence.
● Control Statements. ● If statement ● Nested ifs
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Arithmetic Operators
● Java operators can be divided into four groups: arithmetic, bitwise, relational, and logical.
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Arithmetic Operators
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Example 1
} }
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Example 1
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Example 2
Prefix &Postfix operator
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• The increment operators used to adds 1 to previous value. Increment operator is unary operator because only one variable is
used. There are 2 type in increment/decrement operator.
1. Postfix increment operator (variable++) 2. Prefix increment operator (++variable)
Both prefix and postfix increment operator are same thing when they used independently(i++ or ++i) ie adds 1 to previous value.
But they behave differently when they used in expression on the right hand side of assignment statement(num=i++ or num=++i)
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Postfix Example
class group{ public static void main(String arng[]){ int num, i; i=0; i++; num=i++; System.out.println("i="+i); System.out.println("num="+num); } } Output:- i=2 num=1
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Prefix Example
class group{ public static void main(String arng[]){ int num, i; i=0; ++i; num=++i; System.out.println("i="+i); System.out.println("num="+num); } } Output:- i=2 num=2
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Another Example
Prefix: int count=1; System.out.println(++count); displays 2.
Postfix: int count=1; System.out.println(count++); displays 1.
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Relational Operators
The relational operators determine the relationship that one operand has to the other.
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Boolean Logical Operators
The Boolean logical operators operate only on boolean
operands. All of the binary logical operators combine two boolean
values to form a resultant boolean value.
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Boolean Logical Operators
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Example 4
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Example 4
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The Assignment Operator The assignment operator is the single equal sign, =. It has this general form: var = expression; The type of var must be compatible with the type of expression. It allows you to create a chain of assignments. For example, consider this fragment: int x, y, z; x = y = z = 100; // set x, y, and z to 100 This fragment sets the variables x, y, and z to 100 using a single
statement.
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The ? Operator
● Java includes a special ternary (three-way) operator that can replace certain types of if-then-else statements.
● The ? has this general form: expression1 ? expression2 : expression3 ● Here, expression1 can be any expression that evaluates to a boolean
value (condition). ● If expression1 is true, then expression2 is evaluated; otherwise,
expression3 is evaluated. ● The result of the ? operation is that of the expression evaluated.
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Example 5
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Operator Precedence ● Table 1 shows the order of precedence for operators, from highest to lowest.
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Operator precedence
● Evaluate the following expressions:
● 3+5/ 7 answer: 3
● 3*3 +3%2 answer: 10
● 3+2/5+ -2*4 answer: -5
● 3+(2/5)+ (-2*4) answer: -5
● 3*(3+3)%2 answer: 0
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Control Statments ● Control statements are used to cause the flow of execution to
advance and branch based on changes to the state of a program. ● Control Statments include:
● Selection statements allow your program to choose different paths of execution based upon the outcome of an expression or the state of a variable.
● Iteration statements enable program execution to repeat one or more statements (loops).
● Jump statements allow your program to execute in a nonlinear fashion.
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Java’s Selection Statements ● Java supports two selection statements: if and switch. if (condition) statement1; else statement2;
● For example:
int a, b;
if(a < b) a = 0;
else b = 0;
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Nested ifs ● When you nest ifs, remember that an else statement always refers
to the nearest if statement that is within the same block as the else and that is not already associated with an else.
if(i == 10)
{ if(j < 20) a = b;
if(k > 100) c = d; // this if is
else a = c; // astsociated with this else
}
else a = d; // this else refers to if(i == 10)
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The if-else-if Ladder if(condition)
statement;
else if(condition)
statement;
else if(condition)
statement;
...
else
statement; ● The if statements are executed from the top down. As soon as one of the
conditions controlling the if is true, the statement associated with that if is executed, and the rest of the ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
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Program that checks number is zero, positive or negative using if-else-if ladder
class CheckSignNumberDemo { public static void main(String args[]) {
int x = 10; if(x <= -1) System.out.println("x is a negative number having value " + x); else if(x == 0) System.out.println("x is a zero number having value " + x); else if(x > 0) System.out.println("x is a positive number having value " + x);
} }
Example 6
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