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What is += Addition Assignment Operator in Java?

It’s the Addition assignment operator. Let’s understand the += operator in Java and learn to use it for our day to day programming.

x += y in Java is the same as x = x + y.

It is a compound assignment operator. Most commonly used for incrementing the value of a variable since x++ only increments the value by one.

Incrementing Values With the += Operator

This code will increase the value of a by 2. Let’s see the examples:

int a = 1;

On the other hand if we use a++:

int a = 1;

The value of a is increased by just 1.

Using += in Java Loops

The += operator can also be used with for loop:

for(int i=0; i<10; i+=2)

The value of i is incremented by 2 at each iteration.

Working with multiple data types

Another interesting thing to note is that adding int to double using the regular addition expression would give an error in Java.

int a = 1;
a = a + 1.1; // Gives error 
a += 1.1;

The first line here gives an error as int can’t be added to a double. However, when using the += operator in Java, the addition works fine as Java now converts the double to an integer value and adds it as 1.

String Concatenation

The += operator also works for string mutation.

String a = "Hello";

The string “Hello” has been mutated and the string “World” has been concatenated to it.


The += is an important assignment operator. It is most commonly used with loops. The same assignment also works with other operators like -=, *=, /=.

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