What is the best way to create a singleton class in java?

Question

What is the best way to create a singleton class in java?

Answer 1

Here are a few of the singleton design pattern constructs. As to which is best, it depends on how you're using it and is otherwise subjective.

// Lazy Initialization
public class Singleton {
private static Singleton instance = null;

private Singleton() {}

public static Singleton getInstance() {
if(instance == null) {
instance = new Singleton();
}
return instance;
}
}

// Thread safe
public class Singleton {
private static Singleton instance;

private Singleton() {}

public static synchronized Singleton getInstance() {
if(instance == null) {
instance = new Singleton();
}
return instance;
}
}

//Thread safe with locking
public class Singleton {
private static Singleton instance;

private Singleton() {}

public static Singleton getInstance() {
if(instance == null) {
synchronized (Singleton.class) {
if(instance == null) {
instance = new Singleton();
}
}
}
return instance;
}
}

// Helper class "Bill Pugh"
public class Singleton {
private Singleton() {}

private static class SingletonHelper {
private static final Singleton INSTANCE = new Singleton2();
}

public static Singleton getInstance() {
return SingletonHelper.INSTANCE;
}
}

// Eager Initialization
public class Singleton {
private static final Singleton INSTANCE = new Singleton();

private Singleton() {}

public static Singleton getInstance() {
return INSTANCE;
}
}

// Static Block
public class Singleton {
private static Singleton instance;

private Singleton() {}

static {
instance = new Sigleton();
}

public static Singleton getInstance() {
return instance;
}

}

Answer 2

More info:
https://www.google.com/amp/s/www.journaldev.com/1377/java-singleton-design-pattern-best-practices-examples/amp

Answer 3

i asked for creation of a singleton

Answer 4

Google Design Patterns for Java.