Java - if-else Statement

Java if-else Statement

In Java, the if else statement is used to execute two code blocks based on the given condition. A Java if statement executes when the Boolean expression for the if statement is true. An if statement can be followed by an optional else statement, which executes when the Boolean expression is false.

Syntax of if-else Statement in Java

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 of if-else Statement in Java

Example: Java if else statement

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

Java if-else-if Statement

The if...else if...else statement is used for executing multiple code blocks based on the given conditions (Boolean expressions).

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

Points to Remember

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 of if-else-if statement

Following is the syntax of an if...else 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 1: Java if … else if … else statement

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 2: Java if … else if … else statement

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

Java Nested if-else Statement

The nested if else statement is used for better decision-making when other conditions are to be checked when a given condition is true. In the nested if else statement, you can have an if-else statement block the another if (or, else) block.

Syntax of nested if-else statement

Below is the syntax of nested if else statement:

if(condition1){    
	// code block    
	if(condition2){  
		//code block
	}    
}

Example: Java Nested if else Statement

The following examples finds the largest number among three using nested if..else statement.

public class Test {

    public static void main(String[] args) {

        int x = 10, y = 20, z = 30;

        if(x >= y) {
            if(x >= z)
                System.out.println(x + " is the largest.");
            else
                System.out.println(z + " is the largest.");
        } else {
            if(y >= z)
                System.out.println(y + " is the largest.");
            else
                System.out.println(z + " is the largest.");
        }
    }
}

Output

30 is the largest.