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Java - if-else statement


An if statement can be followed by an optional else statement, which executes when the Boolean expression is false.

Syntax

Following is the syntax of an if...else statement −

if(Boolean_expression) {
   // Executes when the Boolean expression is true
}else {
   // Executes when the Boolean expression is false
}

If the boolean expression evaluates to true, then the if block of code will be executed, otherwise else block of code will be executed.

Flow Diagram

If Else Statement

Example 1

In this example, we're showing the usage of if else statement. We've created a variable x and initialized it to 30. Then in the if statement, we're checking x with 20. As if statement is false, the statement within the else block is executed.

public class Test {

   public static void main(String args[]) {
      int x = 30;

      if( x < 20 ) {
         System.out.print("This is if statement");
      }else {
         System.out.print("This is else statement");
      }
   }
}

Output

This is else statement

The if...else if...else Statement

An if statement can be followed by an optional else if...else statement, which is very useful to test various conditions using single if...else if statement.

When using if, else if, else statements there are a few points to keep in mind.

  • An if can have zero or one else's and it must come after any else if's.

  • An if can have zero to many else if's and they must come before the else.

  • Once an else if succeeds, none of the remaining else if's or else's will be tested.

Syntax

Following is the syntax of an if...else statement −

if(Boolean_expression 1) {
   // Executes when the Boolean expression 1 is true
}else if(Boolean_expression 2) {
   // Executes when the Boolean expression 2 is true
}else if(Boolean_expression 3) {
   // Executes when the Boolean expression 3 is true
}else {
   // Executes when the none of the above condition is true.
}

Example 2

In this example, we're showing the usage of if...else if...else statement. We've created a variable x and initialized it to 30. Then in the if statement, we're checking x with 10. As if statement is false, control jumps to else if statement checking another value with x and so on.

public class Test {

   public static void main(String args[]) {
      int x = 30;

      if( x == 10 ) {
         System.out.print("Value of X is 10");
      }else if( x == 20 ) {
         System.out.print("Value of X is 20");
      }else if( x == 30 ) {
         System.out.print("Value of X is 30");
      }else {
         System.out.print("This is else statement");
      }
   }
}

Output

Value of X is 30

Example 3

In this example, we're showing the usage of if...else if...else statement. We've created a variable x and initialized it to 30.0. Then in the if statement, we're checking x with 10,0. As if statement is false, control jumps to else if statement checking another value with x and so on.

public class Test {

   public static void main(String args[]) {
      double x = 30.0;

      if( x == 10.0 ) {
         System.out.print("Value of X is 10.0");
      }else if( x == 20.0 ) {
         System.out.print("Value of X is 20.0");
      }else if( x == 30.0 ) {
         System.out.print("Value of X is 30.0");
      }else {
         System.out.print("This is else statement");
      }
   }
}

Output

Value of X is 30.0
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