Unary Operator Basics

In math, we sometimes put symbols before numbers to denote something about them. For example, we put the ‘-‘ sign before numbers below 0, and we can put the ‘+’ symbol to denote numbers above 0.

In Java, we can do the same thing, and a little more. Java has what are called ‘Unary Operators’. Unary operators allow you to perform some operation on a number. Unlike arithemetic operators, unary operators perform an operation on one number or variable, not two.

Let’s look at some examples.


In this example, we want to show that the variable positive is positive 1, and the variable negative is negative 2:

int positive = +1;
int negative = -2;

It should be noted that positive numbers do not require the unary operator + to be interpreted as positive by Java.


There are more unary operators that perform calculations on numbers:

int num1 = 1;
int num2 = 2;

num1++; // this adds one to num1
num2--; // this subtracts one from num2


If you are working with booleans (true or false expressions), you can negate the value of the boolean by using the ! unary operator. Here are a few examples:

boolean isTired = true;
boolean isAwake = false;
if (! isTired){ // if isTired is false
    isAwake = true;
}

To learn more, visit the Java tutorials.