Java Long reverse() Method

The Long.reverse() method in Java is used to reverse the order of the bits in the two's complement binary representation of the specified long value.

Table of Contents

1. Introduction
2. reverse() Method Syntax
3. Examples
   • Reversing Bits of a Positive Long
   • Reversing Bits of a Negative Long
   • Reversing Bits of Zero
4. Real-World Use Case
5. Conclusion

Introduction

The Long.reverse() method is a static method in the Long class in Java. It reverses the order of the bits in the binary representation of the specified long value. This method is useful for various bit manipulation tasks, such as in cryptography, data encoding, and computer graphics.

reverse()() Method Syntax

The syntax for the Long.reverse() method is as follows:

public static long reverse(long i)

• i: The long value whose bits are to be reversed.

The method returns:

• A long value whose bits are the reversed order of the bits in the specified long value.

Examples

Reversing Bits of a Positive Long

The reverse() method can be used to reverse the bits of a positive long value.

Example

public class ReverseBitsExample {
    public static void main(String[] args) {
        long number = 13L; // Binary representation: 0000000000000000000000000000000000000000000000000000000000001101
        long reversed = Long.reverse(number);

        System.out.println("Original binary: " + Long.toBinaryString(number));
        System.out.println("Reversed binary: " + Long.toBinaryString(reversed));
        System.out.println("Reversed long: " + reversed);
    }
}

Output:

Original binary: 1101
Reversed binary: 1010000000000000000000000000000000000000000000000000000000000000
Reversed long: -6917529027641081856

In this example, the binary representation of the long value 13 is reversed, resulting in the long value -6917529027641081856.

Reversing Bits of a Negative Long

The reverse() method can also be used to reverse the bits of a negative long value.

Example

public class ReverseNegativeBitsExample {
    public static void main(String[] args) {
        long number = -13L; // Binary representation: 1111111111111111111111111111111111111111111111111111111111110011
        long reversed = Long.reverse(number);

        System.out.println("Original binary: " + Long.toBinaryString(number));
        System.out.println("Reversed binary: " + Long.toBinaryString(reversed));
        System.out.println("Reversed long: " + reversed);
    }
}

Output:

Original binary: 1111111111111111111111111111111111111111111111111111111111110011
Reversed binary: 1100111111111111111111111111111111111111111111111111111111111111
Reversed long: -3458764513820540929

In this example, the binary representation of the long value -13 is reversed, resulting in the long value -3458764513820540929.

Reversing Bits of Zero

The reverse() method can be used to reverse the bits of zero.

Example

public class ReverseZeroBitsExample {
    public static void main(String[] args) {
        long number = 0L; // Binary representation: 0000000000000000000000000000000000000000000000000000000000000000
        long reversed = Long.reverse(number);

        System.out.println("Original binary: " + Long.toBinaryString(number));
        System.out.println("Reversed binary: " + Long.toBinaryString(reversed));
        System.out.println("Reversed long: " + reversed);
    }
}

Output:

Original binary: 0
Reversed binary: 0
Reversed long: 0

In this example, the binary representation of the long value 0 is reversed, resulting in the long value 0.

Real-World Use Case

Data Encoding

In a real-world application, you might use the Long.reverse() method to reverse bits for data encoding purposes, such as in error detection and correction algorithms.

Example

public class DataEncodingExample {
    public static void main(String[] args) {
        long data = 0b1101011001101L; // Example data in binary
        long encodedData = Long.reverse(data);

        System.out.println("Original data binary: " + Long.toBinaryString(data));
        System.out.println("Encoded data binary: " + Long.toBinaryString(encodedData));
        System.out.println("Encoded data long: " + encodedData);
    }
}

Output:

Original data binary: 1101011001101
Encoded data binary: 1011001101000000000000000000000000000000000000000000000000000000
Encoded data long: -5044031582654955520

In this example, the binary data 0b1101011001101 is reversed for encoding purposes, resulting in the encoded data -5044031582654955520.

Conclusion

The Long.reverse() method in Java is a powerful and useful tool for reversing the order of bits in the binary representation of a long value. By understanding how to use this method, you can efficiently handle tasks that involve bit manipulation in your Java applications. Whether you are dealing with positive or negative long values, or implementing data encoding algorithms, the reverse() method provides a reliable solution for these tasks.