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The Java Lesson 7

Bitwise operations: overview with detailed examples

Overview

Bitwise operations act upon individual bits within integer data. They are used to perform the logical operations AND, OR, and XOR (eXclusive OR), complementing (reversing all bits), and shifting (sliding bits to the left or right).

Logical bitwise operations

• Use the standard boolean operators (&, |, and ^) to act upon two integer values. The short-circuit boolean operators (&& and ||) are not used for bitwise operations and will result in a compile error if attempted.

• Produce an integer result (of size int or larger) that is the logical AND, OR, or XOR of two operands. The rules for these operations are as follows:

Operation	Rule
&	If both corresponding operand bits are "on" the result bit is "on"
|	If either corresponding operand bit is "on" the result bit is "on"
^	If corresponding operand bits are different the result bit is "on"

For example, if

byte x = 5; // Binary value: 0000 0101 Hex value: 05
byte y = 9; // Binary value: 0000 1001 Hex value: 09
byte z;

this table shows the result of executing three unrelated statements. The cast is needed in order to store the int value that results from the operation.

Statement	Binary Result	Hexadecimal	Decimal
z = (byte)(x & y);	0000 0001	01	01
z = (byte)(x | y);	0000 1101	0D	13
z = (byte)(x ^ y);	0000 1100	0C	12

Example: The following program can be run to test logical bitwise operations.

public class App {
public static void main(String[] args) {

// Variables to be read from the user

int first;
int second;

// Prompt for and read the two integers

System.out.print("First integer: ");
first = Keyboard.readInt();
System.out.print("Second integer: ");
second = Keyboard.readInt();

// Display the results of logical bitwise operations

System.out.println(" " + first + " & " + second + " = " +
(first & second));
System.out.println(" " + first + " | " + second + " = " +
(first | second));
System.out.println(" " + first + " ^ " + second + " = " +
(first ^ second));
}
}

Notes:

1. Program results are displayed in decimal. To really understand what is happening, work out the equivalent binary and hexadecimal values.

2. Be sure to run the program several times with different integer values.

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