Java : Checksum with Examples

final byte[] b = "abcd".getBytes();
System.out.println(Arrays.toString(b)); // [97, 98, 99, 100]

{
    final Checksum checksum = new CRC32();

    checksum.update(b);
    System.out.printf("%x%n", checksum.getValue()); // ed82cd11
}
{
    final Checksum checksum = new Adler32();

    checksum.update(b);
    System.out.printf("%x%n", checksum.getValue()); // 3d8018b
}

long getValue ()

Returns the current checksum value.

final var b = "abcd".getBytes();
System.out.println(Arrays.toString(b)); // [97, 98, 99, 100]

final Checksum checksum = new CRC32();

checksum.update(b);
System.out.printf("%x%n", checksum.getValue()); // ed82cd11

final Checksum checksum = new CRC32();

checksum.update(97);
System.out.printf("%x%n", checksum.getValue()); // e8b7be43

checksum.update(98);
System.out.printf("%x%n", checksum.getValue()); // 9e83486d

checksum.update(99);
System.out.printf("%x%n", checksum.getValue()); // 352441c2

checksum.update(100);
System.out.printf("%x%n", checksum.getValue()); // ed82cd11

void reset ()

Resets the checksum to its initial value.

final Checksum checksum = new CRC32();
System.out.printf("%x%n", checksum.getValue()); // 0

checksum.update("abcd".getBytes());
System.out.printf("%x%n", checksum.getValue()); // ed82cd11

checksum.reset();
System.out.printf("%x%n", checksum.getValue()); // 0

default void update (byte[] b)

Updates the current checksum with the specified array of bytes.

Please see getValue().

void update (byte[] b, int off, int len)

Updates the current checksum with the specified array of bytes.

final var b = "abcdXYZ".getBytes();
System.out.println(Arrays.toString(b)); // [97, 98, 99, 100, 88, 89, 90]

final Checksum checksum = new CRC32();

checksum.update(b, 0, 4);
System.out.printf("%x%n", checksum.getValue()); // ed82cd11

checksum.reset();
checksum.update(b, 4, 3);
System.out.printf("%x%n", checksum.getValue()); // 7d29f8ed

final Checksum checksum = new CRC32();

checksum.update("abcd".getBytes());
System.out.printf("%x%n", checksum.getValue()); // ed82cd11

checksum.reset();
checksum.update("XYZ".getBytes());
System.out.printf("%x%n", checksum.getValue()); // 7d29f8ed

void update (int b)

Updates the current checksum with the specified byte.

Please see getValue().

default void update (ByteBuffer buffer)

Updates the current checksum with the bytes from the specified buffer.

final var buffer = ByteBuffer.wrap("abcd".getBytes());
System.out.println(buffer); // java.nio.HeapByteBuffer[pos=0 lim=4 cap=4]

final Checksum checksum = new CRC32();

checksum.update(buffer);
System.out.printf("%x%n", checksum.getValue()); // ed82cd11

System.out.println(buffer); // java.nio.HeapByteBuffer[pos=4 lim=4 cap=4]