How to Create GUID in Java

1. What Is GUID
2. Example Code to Generate UUID Using randomUUID() Method
3. Example Code to Generate UUID Using UUID constructor and fromString() Method

What Is GUID

GUID is an acronym for Globally Unique Identifier. It is often also referred to Universally Unique Identifiers or UUIDs. There is no genuine difference between the two terms. Technically, these are 128-bit immutable, unique, cryptographically-strong, random numbers. These random numbers are eventually in use for computing purposes. The algorithm to generate such numbers is so complex that it could generate 1,0000,000,000 random numbers per second. These numbers are unlikely to repeat.

We use GUID or UUIDs in software development practices and methodologies, where we would like huge transactions to happen with a unique ID as a primary key that is database keys, component identifiers, and varied transactions.

Example Code to Generate UUID Using randomUUID() Method

package guid;

import java.util.UUID;

public class CreateGuid {
  public static void main(String[] args) {
    UUID uuid = UUID.randomUUID();
    System.out.println("UUID = " + uuid.toString());
  }
}

In Java language, the UUID class is available after version 1.5. The class is present in the java.util.UUID package. The randomUUID() method is a static factory method to retrieve a type 4 (pseudo-randomly generated) UUID. As the method is a static factory method of the UUID class hence the class name is required to call the method.

The output from the above program seems to be a uniquely generated UUID.

UUID = 70aba303-60d8-4cb5-b3e7-4170c4be5642

Example Code to Generate UUID Using UUID constructor and fromString() Method

In the below program, the UUID class constructor is used to generate a UUID. The constructor takes two parameters, mostSignificantBits and leastSignificantBits.

The mostSignificantBits is for the most significant 64 bits of the UUID, and the leastSignificantBits is for the least significant 64 bits.

The fromString() method is a static factory method that creates a UUID from the string standard representation. The above method takes String as a parameter. So over the uuid object, the toString() method is called in the inline function.

The fromString method throws IllegalArgumentException if the name does not conform to the string representation described in the toString method.

package guid;

import java.util.UUID;

public class GenerateGuidUsingConstructor {
  public static void main(String[] args) {
    UUID uuid = new UUID(24, 02);
    System.out.println(UUID.fromString(uuid.toString()));
  }
}

Below is the output of the UUID generated from the constructor.

00000000-0000-0018-0000-000000000002