Singleton Pattern

Poorna Senani Gamage — Sat, 18 Jan 2020 10:13:10 +0000

Singleton pattern is the simplest pattern in java and is under the creational pattern. some key points to use in singleton pattern.

It is static in nature
private constructor
private static instance of the class
public static getter method
no parameters to the constructor

create singleton class

public class Singleton {
    private static Singleton object = null;
    private Singleton() {
    }
    public static Singleton getInstance() {
        if (object == null) {
            object = new Singleton();
        }
        return object;
    }
    public void showMessage() {
        System.out.println("Singleton Pattern");
    }
}

create demo class

public class Demo {
    public static void main(String[] args) {
        Singleton object = Singleton.getInstance();
        object.showMessage();
    }
}

but this classic implementation not thread safe. therefore using synchronized make sure that the one thread can execute the getInstance();at one time.
As this;

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

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Singleton Pattern