3. Numeric Data and Operators

3.4. Assignment Operators

In addition to the simple assignment operator (=), Java supplies a number of shortcut assignment operators that allow you to combine an arithmetic operation and an assignment in one operation. These operations can be used with either integer or floating-point operands. For example, the += operator allows you to combine addition and assignment into one expression. The statement

k += 3;

is equivalent to the statement

k = k + 3;

Similarly, the statement

r += 3.5 +2.0 * 9.3 ;

is equivalent to

r = r + (3.5 + 2.0 * 9.3); // i.e., r = r + 22.1;

As these examples illustrate, when using the += operator, the expression on its right-hand side is first evaluated and then added to the current value of the variable on its left-hand side.

Table 5.8 lists the other assignment operators that can be used in combination with the arithmetic operators. 

Table 5.8 Java's assignment operators

Operator  Operation  Example  Interpretation 
= Simple assignment  m=n; m=n;
+= Addition then assignment  m+=3; m=m+3;
-= Subtraction then assignment m-=3; m=m-3;
*= Multiplication then assignment  m*=3; m=m*3;
/= Division then assignment m/=3; m=m/3;
%= Remainder then assignment m%=3; m=m%3;

For each of these operations, the interpretation is the same: Evaluate the expression on the right-hand side of the operator and then perform the arithmetic operation (such as addition or multiplication) to the current value of the variable on the left of the operator.