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How to use Increment and Decrement operator in Java ?.

Updated on September 17, 2014

Introduction -

In this tutorial, you will learn how to use increment and decrement operators in Java. Increment (++) and decrement (--) operators in Java are unary operators. They are termed as unary operators because they perform manipulation on single operand. Increment operator increase value of an operand by one. Decrement operator decrease value of an operand by one. Increment and decrement operators are of two flavors : Prefix form and Postfix form.

Prefix form - ( ++x ) or ( --x ). In Prefix form increment or decrement operator comes before the variable. In Prefix form value of variable is increased or decreased by one and than variable is used.

Postfix form - ( x++ ) or ( x-- ). In Postfix form increment or decrement operator comes after the variable. In Postfix form value of variable is used first and than increased or decreased by one.

They are used to demonstrate shorthand version of various steps together. It helps in saving few lines of code. In this tutorial, you will find a complete video tutorial and highly commented Java source code demonstrating concept of increment and decrement operator in Java.

Increment and Decrement Operator in Java.
Increment and Decrement Operator in Java.

Java video tutorial - How to use increment and decrement operator in Java ?

Java Source Code - Eclipse Snapshot

How to use increment and decrement operator in Java ?.
How to use increment and decrement operator in Java ?.

Java source code - How to use increment and decrement operator in Java.

// Create a Java class. Here, in our case it is 'IncrementAndDecrementDemo'.
public class IncrementAndDecrementDemo {

	// Create a main method to demonstrate working of Increment and 
	// Decrement operator in Java.
	public static void main(String[] args) {

		// Create two integer variables x and y. Assign a value say 10 to x.
		int x = 10;		
		int y;

		// Apply prefix form of increment operator over x and assign result
		// to y.
		y = ++x;

		// After applying prefix form of increment operator over x and y, print the values on the Java 
		// console.
		System.out.println("The values of x and y in prefix form (increment) are : x = " + x + " and y = " + y );

		// Assign a value say 10 to x.
		x = 10;

		// Apply prefix form of decrement operator over x and assign result
		// to y.
		y = --x;

		// After applying prefix form of decrement operator over x and y, print the values on the Java 
		// console.
		System.out.println("The values of x and y in prefix form (decrement) are : x = " + x + " and y = " + y );

		// Assign a value say 10 to x.
		x = 10;		

		// Apply postfix form of increment operator over x and assign result
		// to y.
		y = x++;

		// After applying postfix form of increment operator over x and y, print the values on the Java 
		// console.
		System.out.println("The values of x and y in postfix form (increment) are : x = " + x + " and y = " + y );

		// Assign a value say 10 to x.
		x = 10;		

		// Apply postfix form of decrement operator over x and assign result
		// to y.
		y = x--;

		// After applying postfix form of decrement operator over x and y, print the values on the Java 
		// console.
		System.out.println("The values of x and y in postfix form (decrement) are : x = " + x + " and y = " + y );

	}

}

Steps to implement -

Step 1 - Create a Java class. Here, in our case it is 'IncrementAndDecrementDemo'.

Step 2 - Create a main method to demonstrate working of Increment and Decrement operator in Java.

Step 3 - Create two integer variables x and y. Assign a value say 10 to x.

Step 4 - Apply prefix form of increment operator over x and assign result to y.

Step 5 - After applying prefix form of increment operator over x and y, print the values on the Java console.

Step 6 - Again, assign a value say 10 to x.

Step 7 - Apply prefix form of decrement operator over x and assign result to y.

Step 8 - After applying prefix form of decrement operator over x and y, print the values on the Java console.

Step 9 - Again, assign a value say 10 to x.

Step 10 - Apply postfix form of increment operator over x and assign result to y.

Step 11 - After applying postfix form of increment operator over x and y, print the values on the Java console.

Step 12 - Again, assign a value say 10 to x.

Step 13 - Apply postfix form of decrement operator over x and assign result to y.

Step 14 - After applying postfix form of decrement operator over x and y, print the values on the Java console.

Output of the program -

The values of x and y in prefix form (increment) are : x = 11 and y = 11
The values of x and y in prefix form (decrement) are : x = 9 and y = 9
The values of x and y in postfix form (increment) are : x = 11 and y = 10
The values of x and y in postfix form (decrement) are : x = 9 and y = 10

Output of the program - Eclipse Snapshot

Output of the program - How to use increment and decrement operator in Java ?.
Output of the program - How to use increment and decrement operator in Java ?.

Output of the program - Explanation

In first case (++x), prefix increment operator first increments value of x to 11 and than assign that value to y. So, value of x and y prints on the Java console as, x = 11 and y = 11.

In second case (--x), prefix decrement operator first decrements value of x to 9 and than assign that value to y. So, value of x and y prints on the Java console as, x = 9 and y = 9.

In third case (x++), postfix increment operator first assign value of x to y and than increments value of x to 11. So, value of x and y prints on the Java console as, x = 11 and y = 10.

In fourth case (x--), postfix decrement operator first assign value of x to y and than decrements value of x to 9. So, value of x and y prints on the Java console as, x = 9 and y = 10.

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