Java Tutorial 8: Operators-Assignment, Arithmetic, and Unary Operators

The Simple Assignment Operator

One of the most common operators that you'll encounter is the simple assignment operator "=". You saw this operator in the Bicycle class; it assigns the value on its right to the operand on its left:

 int cadence = 0;

 int speed = 0;

 int gear = 1;

This operator can also be used on objects to assign object references, as discussed in Creating Objects.

The Arithmetic Operators

The Java programming language provides operators that perform addition, subtraction, multiplication, and division. "%" divides one operand by another and returns the remainder as its result.

+       additive operator (also used for  String concatenation)

-       subtraction operator

*       multiplication operator

/       division operator

%      remainder operator,

You can combine the arithmetic operators with the simple assignment operator to create compound assignments. For example, x+=1; and x=x+1; both increment the value of x by 1. The + operator can also be used for concatenating (joining) two strings together, as shown in the following ConcatDemo program:

The Unary Operators

The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression, or inverting the value of a boolean.

+       Unary plus operator; indicates positive value (numbers are positive without this)

-       Unary minus operator; negates

++      Increment operator; increments   a value by 1

--      Decrement operator; decrements a value by 1

!       Logical complement operator;  inverts the value of a boolean

The increment/decrement operators can be applied before (prefix) or after (postfix) the operand. The code result++; and ++result; will both end in result being incremented by one. The only difference is that the prefix version (++result) evaluates to the incremented value, whereas the postfix version (result++) evaluates to the original value. If you are just performing a simple increment/decrement, it doesn't really matter which version you choose. But if you use this operator in part of a larger expression, the one that you choose may make a significant difference.

The following program, PrePostDemo, illustrates the prefix/postfix unary increment operator:

class PrePostDemo {

    public static void main(String[] args){

        int i = 3;

        i++;

        // prints 4

        System.out.println(i);

        ++i;                                                  

        // prints 5

        System.out.println(i);

        // prints 6

        System.out.println(++i);

        // prints 6

        System.out.println(i++);

        // prints 7

        System.out.println(i);

    }

}