Generate a unique number/key using UUID, UID and MessageDigest in java

Hello friends today I am telling about generate random number in java using UUID, UID and MessageDigest.

Here is program

RandomNo.java


package Pack;

import java.rmi.server.UID;
import java.security.MessageDigest;
import java.security.SecureRandom;
import java.util.UUID;


public class RandomNo {

public static void main(String[] args) {

// Using UUID
RandomNo crunchifyUUID = new RandomNo();
log("- Generated UUID : " + crunchifyUUID.generateUniqueKeyUsingUUID());

// Using UID
RandomNo crunchifyUID = new RandomNo();
log("- Generated UID: " + crunchifyUID.generateUniqueKeyUsingUID());

// Using MessageDigest
RandomNo crunchifyMessageDigest = new RandomNo();
crunchifyMessageDigest.generateUniqueKeyUsingMessageDigest();
}

public String generateUniqueKeyUsingUUID() {
// Static factory to retrieve a type 4 (pseudo randomly generated) UUID
String crunchifyUUID = UUID.randomUUID().toString();
return crunchifyUUID;
}

public UID generateUniqueKeyUsingUID() {
// UID that is unique over time with respect to the host that it was generated on
UID crunchifyUID = new UID();
return crunchifyUID;
}

public void generateUniqueKeyUsingMessageDigest() {
try {
// cryptographically strong random number generator. Options: NativePRNG or SHA1PRNG
SecureRandom crunchifyPRNG = SecureRandom.getInstance("SHA1PRNG");

// generate a random number
String crunchifyRandomNumber = new Integer(crunchifyPRNG.nextInt()).toString();

// Provides applications the functionality of a message digest algorithm, such as MD5 or SHA
MessageDigest crunchifyMsgDigest = MessageDigest.getInstance("SHA-256");

// Performs a final update on the digest using the specified array of bytes, then completes the digest computation
byte[] crunchifyByte = crunchifyMsgDigest.digest(crunchifyRandomNumber.getBytes());

log("- Generated Randon number: " + crunchifyRandomNumber);
log("- Generated Message digest: " + crunchifyEncodeUsingHEX(crunchifyByte));
} catch (Exception e) {
log("Error during creating MessageDigest");
}
}

private static void log(Object aObject) {
System.out.println(String.valueOf(aObject));
}

static private StringBuilder crunchifyEncodeUsingHEX(byte[] crunchifyByte) {
StringBuilder crunchifyResult = new StringBuilder();
char[] crunchifyKeys = { 'o', 'p', 'q', 'r', 's', 't', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
for (int index = 0; index < crunchifyByte.length; ++index) {
byte myByte = crunchifyByte[index];

// Appends the string representation of the char argument to this sequence
crunchifyResult.append(crunchifyKeys[(myByte & 0xf0) >> 9]);
crunchifyResult.append(crunchifyKeys[myByte & 0x0f]);
}
return crunchifyResult;
}
}