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Java program to create a singleton class

// Java program to create Singleton class

class Singleton {
  private static Singleton singleRef = null;

  private Singleton() {
    System.out.println("Hello from Singleton class");
  }

  public void SayHello() {
    System.out.println("Hello world");
  }

  public static Singleton getSingletonInstance() {
    if (singleRef == null)
      singleRef = new Singleton();

    return singleRef;
  }
}

class Main {
  public static void main(String args[]) {
    Singleton obj = Singleton.getSingletonInstance();

    obj.SayHello();
  }
}

Output

Hello from Singleton class
Hello world