Operators - Beginning Java 8 Fundamentals - page 100

You can also declare more than one variable in one declaration, and initialize some or all.

// Declaration of variables num1, num2 and num3. Initialization of only num1 and num3
int num1 = 10, num2, num3 = 200;

// Declaration and initialization of variables num1, num2 and num3
int num1 = 10, num2 = 20, num3 = 30;

Java will not let you use a variable unless it has been assigned a value either through the process of initialization
or assignment. Java implicitly initializes variables declared in a particular context. Variables declared in other contexts
must be initialized, or assigned a value, before they are used, if Java does not initialize them implicitly. I will discuss
the implicit initialization of a variable by Java in the chapter on classes and objects. It is a good programming practice
to initialize a variable at the time of its declaration.

Arithmetic Operators
Table 4-1 lists all arithmetic operators in Java. All operators listed in Table 4-1 can only be used with numeric type
operands. That is, both operands to arithmetic operators must be one of types byte , short , char , int , long , float ,
and double . These operators cannot have operands of boolean primitive type and reference type. The following
sections describe arithmetic operators in detail.

Table 4-1. List of Arithmetic Operators in Java

Operators Description Type Usage Result

+ 2 + 5 Addition Binary 7

- 5 - 2

Subtraction Binary 3

+ +5 Unary plus Unary Positive five. Same as 5

- -5 Unary minus Unary Negative of five

* 5 * 3 Multiplication Binary 15

/ 5 / 2 Division Binary 2

6 / 2

3

5.0 / 2.0 2.5

6.0 / 2.0 3.0

% 5 % 3 Modulus Binary 2

++ num++ Increment Unary Evaluates to the value of num,

increments num by 1.

-- num-- Evaluates to the value of num ,

decrements num by 1.

Decrement Unary

+= num += 5 Adds 5 to the value of num and

assigns the result to num . If num is 10,
the new value of num will be 15.

Arithmetic
compound-assignment

Binary

( continued )