A Guide to Increment and Decrement Unary Operators in Java

1. Overview

In this tutorial, we’ll briefly discuss the increment and decrement unary operators in Java.

We’ll start by looking at the syntax followed by the usage.

2. Increment and Decrement Operations in Java

In Java, the increment unary operator increases the value of the variable by one while the decrement unary operator decreases the value of the variable by one.

Both update the value of the operand to its new value.

The operand required should be a variable that is not constant, as we wouldn’t be able to modify its value. Furthermore, the operand can’t be an expression because we cannot update them.

The increment and decrement unary operators have two forms, which are, prefix and postfix.

3. Pre-Increment and Pre-Decrement Unary Operators

In the prefix form, the increment and decrement unary operators appear before the operand.

While using the prefix form, we first update the value of the operand and then we use the new value in the expression.

First, let’s look at a code snippet using the pre-increment unary operator:

int operand = 1;
++operand; // operand = 2
int number = ++operand; // operand = 3, number = 3

Next, let’s have a look at the code snippet using the pre-decrement one:

int operand = 2;
--operand; // operand = 1
int number = --operand; // operand = 0, number = 0

As we see, the prefix operators change the value of the operand first, and then the rest of the expression gets evaluated. This can easily lead to confusion if embedded in a complex expression. It’s recommended we use them on their own line rather than in larger expressions.

4. Post-Increment and Post-Decrement Unary Operators

In the postfix form, the operator appears after the operand.

While using the postfix form, we first use the value of the operand in the expression and then update it.

Let’s look at a sample code snippet using the post-increment operator:

int operand = 1;
operand++; // operand = 2
int number = operand++; // operand = 3, number = 2

Also, let’s have a look at the post-decrement one:

int operand = 2;
operand--; //operand = 1
int number = operand--; // operand = 0, number 1

Similarly, post-increment and post-decrement unary operators should be on their own line rather than including them in larger expressions.

5. Conclusion

In this quick tutorial, we learned about the increment and decrement unary operators in Java. Moreover, we looked at their two forms: prefix and postfix. Finally, we looked at its syntax and sample code snippets.

The full source code of our examples here is, as always, over on GitHub.