Java Operators

Operators are special symbols used to perform specific operations on one or more objects. They are the basic way of manipulating data.

Java has several categories of operators based on their functionality.

Operands

Before describing the various operators used in Java, we need to know the terminology. Every operator requires one or two operands. If the operand appears to the left of the operator, it is called a left operand. If the operand appears to the right of the operator, it is called a right operand.

An operand is a constant, a variable/object, or an expression. An operand, with its left and right operands forms an expression and the value of the expression is the results of the operator. An expression is always evaluated and the resulting value is used.

Use of parentheses

Parentheses, "()", are used to define the order in which operations are performed. There are rules that define the order of operations when parentheses are not used. It is easy to make mistakes on what the order of operations will result in so the use of parentheses makes the code easier to control.

Will 2 + 3 * 4 evaluate to 20 or 14? Using parentheses makes it easier to read the code. In other words, (2 + 3) * 4 is 20 while 2 + (3 * 4) is 14.

Based on Java's order of operations, the expression 2 + 3 * 4 is 14 because * has a higher order than + and is done first. Operators at the same level or order are evaluated left to right.

Arithmetic Operators

As the name implies, arithmetic operators perform mathematical functions. These operators take two variables, called operands, and performs the appropriate mathematical operations. Neither of the operands are changed. The results of the mathematical operation is used in place of the expression.

Note: Operands are referred to left operand and right operand based on which side of the operator they reside.

Table 1: Arithmetic Operators

Assignment Operators

Assignment operators are used to set a value to the left operand. There may be additional mathematical operations performed to determine what the value is.

In a sense, there is only one assignment operator and it is the =. The rest of the assignment operators use two symbols, a mathematical operator and the =. These are short cuts for A Z= B ==> A = (A Z B) where Z is the mathematical operator. In these cases, the value is obtained using the origanal value of the left operand, A in this case.

Note: Restriction: The left operator of an assignment operator must be a variable or object. It cannot be a constant or an expression because the value of a constant or an expression cannot be changed.

Table 2: Assignment Operators

Boolean Operators

Boolean operators perform boolean operations on two operands. When an expression using boolean operators is evaluated, the results is either true or false.

Table 3: Boolean Operators

Logical Operators

Logical operators performs boolean operations on boolean operands or expressions that evaluate to a boolean value.

The evaluation of a logical operator expression only returns true or false.

Logical operators do not change any variable or object. They just return a boolean value.

Table 4: Logical Operators

Unary Operators

Unary Operators operator on a single operand. The behavior of the operation will vary depending on whether the operand is a left or right operand.

Both the increment and decrement operators will change the value of its operand.

Table 5: Unary Operators

Bitwise Operators

Bitwise operators operate on the individual bits of an integer variable. The operation is performed on each bit in the operand and the bit in the same position in the other operand. The results of a bitwise operation is to set each bit in the resulting value to either 1 or 0.

In Java, the order of bits goes from the MSB is on the left and the LSB is on the right. If you were to number the positions of the bits, the LSB, a.k.a. the Least Significant Bit, is in position 0. The position of each bit to the left increments by 1 until reaching ther MSB, a.k.a. the Most Significant Bit, is in position (N - 1) where N is the number of bits in the unit of memory.

When the unit of memory holds a signed integer, the MSB holds the sign bit. It is 0 for positive numbers and 1 for negative numbers. This is important with the bit shifting operators.

Table 6: Bitwise Operators

Ternary (Conditional) Operator

Unlike the other operators, the ternary operator takes three operands. This operator is basically shorthand for a simple:

if (condition) valueIfTrue else valueIfFalse

Where condition is a boolean expression and valueIfTrue and valueIfFalse are expressions to be evaluated.

The syntax of this operator is

condition _? valueIfTrue : valueIfFalse

The primary use of the ternary operator is provide a notation that allows a value that is depended on a boolean expression to be used where a temporary variable would be needed.

Exampe:

int value = 0;

if ( A && B )
{
    value = C + D;
}
else
{
    value = C - D;
}

foobar(value);

verses this

foobar( (A && B) ? (C + D) : (C - D) );

Order of Operators

This tutorial will not go into the order of operators. This information is available on the web by searching Java Order of Operators.

The following are some references:

• Operator Precedence in Java
• Java Operator Precedence Table

References

The following links provide more information on Java Operators.

• Java Operators - w3school
• Java Operators - GeeksforGeeks