Combined assignment operators

Consider the following fragment of a Java program:

int sum, a, salary, increase;
sum = sum + a;
salary = salary * increase;

It can be abbreviated as follows:

sum += a;
salary *= increase;

In general, the assignment:

x = x operator expression

can be abbreviated as:

x operator= expression

For each of the arithmetic operators +, -, *, /, %, there is the corresponding combined assignment operator +=, -=, *=, /=, %=.