How to Convert Long to Byte Array and Back in Java?

Converting Long to Byte Array and Back in Java

When transmitting data over a TCP connection, it may be necessary to convert a long to a byte array. To achieve this conversion, you can leverage the following methods:

<code class="java">public byte[] longToBytes(long x) {
    ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
    buffer.putLong(x);
    return buffer.array();
}

public long bytesToLong(byte[] bytes) {
    ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
    buffer.put(bytes);
    buffer.flip();
    return buffer.getLong();
}</code>

To avoid excessive creation of ByteBuffers, consider utilizing a class like the one below:

<code class="java">public class ByteUtils {
    private static ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);    

    public static byte[] longToBytes(long x) {
        buffer.putLong(0, x);
        return buffer.array();
    }

    public static long bytesToLong(byte[] bytes) {
        buffer.put(bytes, 0, bytes.length);
        buffer.flip();
        return buffer.getLong();
    }
}</code>

Remember, it's often preferable to employ a library like Guava for this task. However, for native Java solutions, these methods provide a reliable way to handle long-to-byte array conversions.

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