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Java Bitwise Operators



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Java provides several bitwise operators that can be applied to the integer types: long, int, short, char, and long. These operators act upon the individual bits of their operands.

Java Bitwise Operators List

The Java Bitwise Operators are summarized here in this table :

Operator Name
~ Bitwise unary NOT
& Bitwise AND
| Bitwise OR
^ Bitwise exclusive OR
>> Shift right
>>> Shift right zero fill
<< Shift left
&= Bitwise AND assignment
|= Bitwise OR assignment
^= Bitwise exclusive OR assignment
>>= Shift right assignment
>>>= Shift right zero fill assignment
<<= Shift left assignment

Since, bitwise operators manipulate the bits within an integer, it is important to understand, what effects such manipulations might have on a value. Specifically, it is useful to know, how Java stores integer values and how it represents negative numbers. So, before proceeding, let's briefly review these two topics.

All integer types are represented by binary numbers of varying bit widths. For example, byte value for 42 in binary is 00101010, here each position represents a power of two, starting with 20 at the rightmost bit. The next bit position to the left would be 21, or 2, continuing towards the left with 22, or 4, then 8, 16, 32, and so on. So 42 has 1 bits set at the positions 1, 3, and 5 (counting from 0 at the right); thus, 42 is the sum of 21 + 23 + 25, which is 2 + 8 + 32.

All integer types (except char) are signed integers. This means that they can represent negative values as well as positive ones. Java uses encoding known as two's complement, which means that negative numbers are represented by inverting (converting 1's to 0's and vice-versa) all of the bits in a value, then adding 1 to the result. For example, -42 is represented by inverting all the bits in 42, or 00101010, which yields 11010101, then adding 1, which results in 11010110, or -42. To decode any negative numbers, first invert all of the bits, then add 1. For example, -42, or 11010110 inverted, yields 00101001, or 41, so when you add 1 you get 42.

The reason that Java (and most other computer languages) uses two's complement is easy to see when you consider the issue of zero crossing. Assuming a byte value, zero (0) is represented by 00000000. In one's complement, simply inverting all of the bits creates 11111111, that creates negative zero. The trouble is that negative zero is invalid in integer maths. This problem is solved by using the two's complement to represent the negative values. When using the two's complement, 1 is added to the complement, which producing 100000000. This produces a 1 bit too far to the left to fit back into the byte value, resulting in desired behavior, where -0 is the same as 0, and 11111111 is the encoding for -1. Although we used a byte value in the previous example, the same basic principle applies to all of Java's integer types.

Because Java uses two's complement to store the negative numbers, and because all integers are signed values in Java, applying the bitwise operators can easily produce an unexpected results. For example, turning on the high-order bit will cause the resulting value to be interpreted as negative number, whether this is what you intended or not. To avoid unpleasant surprises, just remember that high-order bit determines the sign of an integer, no matter how that high-order bit gets set.

The Bitwise Logical Operators

The bitwise logical operators are &, |, ^, and ~.

Here this table shows the outcome of each operation. In the discussion that follows, always keep in mind that the bitwise operators are applied to each individual bit within each operand.

A B A | B A & B A ^ B ~A
0 0 0 0 0 1
1 0 1 0 1 0
0 1 1 0 1 1
1 1 1 1 0 0

The Bitwise NOT Operator

The bitwise NOT operator also called the bitwise complement, the unary NOT operator, ~, inverts all of the bits of its operand.

Example

For example, the number 42, which has this bit pattern:

00101010

becomes

11010101

after the NOT operator is applied.

The Bitwise AND Operator

The bitwise AND operator, &, produces a 1 bit if both the operands are also 1. A zero is produced in all the other cases.

Example

Following is an example that demonstrates the bitwise AND operator:

  00101010   42
 &00001111   15
 _________
  00001010   10

The Bitwise OR Operator

The bitwise OR operator, |, combines bits such that if either of the bits in the operands is 1, then the resultant bit is 1.

Example

Following is an example that demonstrates the bitwise OR operator:

 00101010   42
|00001111   15
_________
 00101111   47

The Bitwise XOR Operator

The bitwise XOR operator, ^, combines bits such that if exactly one operand is 1, then the result is 1. Otherwise, the result is zero.

Example

The following example shows the effect of the bitwise XOR (^) operator. This example also demonstrates a useful attribute of a XOR operation. Notice here, how the bit pattern of 42 is inverted wherever the second operand has a 1 bit. Wherever the second operand has 0 bit, the first operand is unchanged. You will find this property useful when performing some types of bit manipulations.

 00101010   42
^00001111   15
_________ 
 00100101   37

The Bitwise Logical Operators Example

The following program demonstrates the bitwise logical operators :

/* Java Program Example - Java Bitwise Operators
*  This program demonstrate the bitwise logical operators */

public class JavaProgram
{   
    public static void main(String args[])
    {
        
        String binary[] = {
            "0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111",
            "1000", "1001", "1010", "1011", "1100", "1110", "1111"
        };
        int a = 3;    // 0 + 2 + 1 or 0011 in binary
        int b = 6;    // 4 + 2 + 0 or 0110 in binary
        int c = a | b;
        int d = a & b;
        int e = a ^ b;
        int f = (~a & b) | (a & ~b);
        int g = ~a & 0x0f;
        
        System.out.println("            a = " + binary[a]);
        System.out.println("            b = " + binary[b]);
        System.out.println("          a|b = " + binary[c]);
        System.out.println("          a&b = " + binary[d]);
        System.out.println("          a^b = " + binary[e]);
        System.out.println("(~a&b)|(a&~b) = " + binary[f]);
        System.out.println("           ~a = " + binary[g]);
        
    }
}

When the above Java program is compile and executed, it will produce the following output:

java bitwise operators

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