Can anyone help me with understanding singleton pls?

Question

it's the sample code used when I learned singleton, but I have no idea how it works.... Thanks in advance

class Test {
private static Test ob;
public static Test getInstance() {
if(ob==null)
ob = new Test();
}
//work
return ob;
}
}

public class Test4 {
public static void main(String[] args) {
Test ob1 = Test.getInstance();
Test ob2 = Test.getInstance();

if (ob1==ob2)
System.out.println("same");
else
System.out.println("different");
}
}

Answer 1

you still need a private constructor to make this work static objects never change; if you have an object that holds a private attr of itself, STATIC, it never changes, therefore a singleton. if you make a private constructor nobody but the class itself can make an instance of it. then when you create a static function in test like you did above, you cna get that static private object in the class, what is indeed the class itself. So there you go: singleton

check https://sourcemaking.com/design_patterns/singleton for singelton patern and others

Answer 2

Ooh, it's great to get some feedback on my help, thank you! Can you mark me as answer if you are satisfied?

Answer 3

Thanks! That helped me a lot!!