Chapter 4- Relational and Logical Operators in Java

Relational Operators in Java

Relational operators are used to evaluate conditions (true or false) inside the if statements.

Some examples of relational operators are:

• == (equals)
• >= (greater than or equals to)
• > (greater than)
• < (less than)
• <= (less than or equals to)
• != (not equals)

Note: ‘=’ is used for assignment whereas ‘==’ is used for equality check.

The condition can be either true or false.

Logical Operators in Java

&&, || and ! are the most commonly used logical operators in Java.

These are read as:

• && - AND
• || - OR
• ! – NOT

The above logical operators are used to provide logic to our Java programs.

• AND Operator

Evaluates to true if both the conditions are true.

• Y && Y = Y                
• Y && N = N
• N && Y = N
• N && N = N

Convention: # Y – True and N - False

• OR Operator

Evaluates to true when at least one of the conditions is true.

• Y || Y = Y                   
• Y || N = Y
• N || Y = Y
• N || N = N

Convention: # Y – True and N - False

• NOT Operator

Negates the given logic (true becomes false and vice-versa)

• !Y = N                         
• !N = Y
• else-if clause

Instead of using multiple if statements, we can also use else if along with if thus forming an if-else-if-else ladder.

Using such kind of logic reduces indents. Last else is executed only if all the conditions fail.

/* if (condition1) {

            //Statements;

else if {

            // Statements;

}

else {

            //Statements

} */

Code as Described in the Video :

package com.company;

public class cwh_17_logical {
    public static void main(String[] args) {
        System.out.println("For Logical AND...");
        boolean a = true;
        boolean b = false;
//        if (a && b){
//            System.out.println("Y");
//        }
//        else{
//            System.out.println("N");
//        }

        System.out.println("For Logical OR...");

//        if (a || b){
//            System.out.println("Y");
//        }
//        else{
//            System.out.println("N");
//        }

        System.out.println("For Logical NOT");
        System.out.print("Not(a) is ");
        System.out.println(!a);
        System.out.print("Not(b) is ");
        System.out.println(!b);
    }
}