Lesson 6: Java Programming in Urdu Hindi - If else statement

The if-then Statement

The if-then statement is the most basic of all the control flow statements. It tells your program to execute a certain section of code only if a particular test evaluates to true.

    if (condition){ 
        do somethingl;
       }
    else{
         do other thing;
                  }

For example, the Bicycle class could allow the brakes to decrease the bicycle's speed only if the bicycle is already in motion. One possible implementation of the applyBrakes method could be as follows:

void applyBrakes() {
    // the "if" clause: bicycle must be moving
    if (isMoving){ 
        // the "then" clause: decrease current speed
        currentSpeed--;
    }
}

The if-then-else Statement

The if-then-else statement provides a secondary path of execution when an "if" clause evaluates to false. You could use an if-then-else statement in the applyBrakes method to take some action if the brakes are applied when the bicycle is not in motion. In this case, the action is to simply print an error message stating that the bicycle has already stopped.

void applyBrakes() {
    if (isMoving) {
        currentSpeed--;
    } else {
        System.err.println("The bicycle has already stopped!");
    } 
}

Nested if

A nested if statement is an if-else statement with another if statement as the if body or the else body.Here's an example:

if ( num > 0 )      // Outer if

  if ( num < 10 )  // Inner if
    
System.out.println( "num is between 0 and 10" ) ;

Here is a example:

class IfElseDemo {
    public static void main(String[] args) {

        int testscore = 76;
        char grade;

        if (testscore >= 90) {
            grade = 'A';
        } else if (testscore >= 80) {
            grade = 'B';
        } else if (testscore >= 70) {
            grade = 'C';
        } else if (testscore >= 60) {
            grade = 'D';
        } else {
            grade = 'F';
        }
        System.out.println("Grade = " + grade);
    }
}