Welcome_To_JavaWorld/code to written at main · polakiganeshkumar/Welcome_To_JavaWorld · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
 singleton thread safe

//lazy initialzation
public class GreatSingleton{

  private static final instance;

  private GreatSingleton(){
  }

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

}


//double checked

public class GreatSingleton{

private static volatile GreatSingleton instance;
private GreatSingleton()
}

public static GreatSingleton getInstance(){
  if(instance == null){ // first check (no locking )
    synchronized(GreatSingleton.class){
      if(instance == null){ // secound check (locked)
        instance=new GreatSingleton();
      }

    }
  }
  return instance;
}


}