ELEMENTARY PROGRAMMING - Introduction to Java Programming - page 54

Caution
There are no spaces in the augmented assignment operators. For example, + = should
be += .

Note
Like the assignment operator ( = ), the operators ( += , -= , *= , /= , %= ) can be used to
form an assignment statement as well as an expression. For example, in the following
code, x += 2 is a statement in the first line and an expression in the second line.

// Statement
System.out.println(

x += 2 ;

x += 2 ); // Expression

2.14 Increment and Decrement Operators
The increment (++) and decrement (- -) operators are for incrementing and
decrementing a variable by 1.

Key
Point

The ++ and —— are two shorthand operators for incrementing and decrementing a variable by 1 .
These are handy, because that's often how much the value needs to be changed in many pro-
gramming tasks. For example, the following code increments i by 1 and decrements j by 1 .

increment operator (++)

decrement operator ( -- )

int i = 3 , j = 3 ;
i++; // i becomes 4
j——; // j becomes 2

i++ is pronounced as i plus plus and i—— as i minus minus. These operators are known as
postfix increment (or postincrement) and postfix decrement (or postdecrement), because the
operators ++ and —— are placed after the variable. These operators can also be placed before
the variable. For example,

postincrement
postdecrement

int i = 3 , j = 3 ;
++i; // i becomes 4
——j; // j becomes 2

++i increments i by 1 and ——j decrements j by 1 . These operators are known as prefix
increment (or preincrement) and prefix decrement (or predecrement).
As you see, the effect of i++ and ++i or i—— and ——i are the same in the preceding exam-
ples. However, their effects are different when they are used in statements that do more than
just increment and decrement. Table 2.5 describes their differences and gives examples.

preincrement
predecrement

T ABLE 2.5

Increment and Decrement Operators

Operator Name Description Example (assume i = 1)

preincrement Increment var by 1 , and use the

new var value in the statement

int j = ++i;
// j is 2, i is 2

++var

postincrement Increment var by 1 , but use the

original var value in the statement

var++ int j = i++;

// j is 1, i is 2

——var predecrement Decrement var by 1 , and use the

new var value in the statement

int j = ——i;
// j is 0, i is 0

postdecrement Decrement var by 1 , and use the

original var value in the statement

var—— int j = i——;

// j is 1, i is 0