Singleton class with lazy and unbreakable

Lazy initialization single ton class

package com.example.practice.student.service;

public class SingletonClassExample {
    private static volatile SingletonClassExample singletonClassExample;

    private SingletonClassExample() {
    }

    public static synchronized SingletonClassExample getInstance() {
        if (singletonClassExample == null) {
            System.out.println("pawankumar");
           return singletonClassExample= new SingletonClassExample();
            //return singletonClassExample = new SingletonClassExample();
        }
        return singletonClassExample;
    }

    public void displayMsg() {
        System.out.println("call from singleton class");
    }

    public static void displayMsg1() {
        System.out.println("call from singleton class");
    }
}

For Eager Initialization on declaration on instance variable  do assignment of object 

private static volatile SingletonClassExample singletonClassExample= new SingletonClassExample();

 unbreakable singleton class

package com.example.practice.student.service;

import java.io.Serializable;

public class UnbreakableSingClass implements Serializable,Cloneable {

    private static  UnbreakableSingClass  unbrak;
    private static boolean objectCreated=false;


    private UnbreakableSingClass UnbreakableSingClass() {
        if(objectCreated) {
            throw new RuntimeException("objet");
        }else {
            return unbrak;
        }
    }

    public static UnbreakableSingClass getIntanance() {
        if(unbrak==null) {
            synchronized (UnbreakableSingClass.class) {
                if(unbrak==null) {
                  return   unbrak=new UnbreakableSingClass();
                }
            }
        }
        return unbrak;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        throw new CloneNotSupportedException("Cloning of this singleton is not allowed.");
    }

    protected Object readResolve() {
        return getIntanance();
    }

}

Java Collection methods.

Collection framework 

List Interface:-

List Interface extends Collection Interface

Collection Interface extends Iterable Interface

1 Iterable Interface Methods

Iterator:-

forEach:-

Collection interface methods:-

List Interface methods:- 

Set interface method:-

Map interface methods:-

Class and inner class example

 public class OuterClass2 {

    private String outerField = "Outer Class Field";

    public void outerMethod() {
        // Local inner class inside a method
        class LocalInnerClass {
            public void display() {
                System.out.println("Accessing outer class field from local inner class: " + outerField);
            }
        }

        // Creating an instance of the local inner class inside the method
        LocalInnerClass localInner = new LocalInnerClass();
        localInner.display();
    }

    public static void main(String[] args) {
        OuterClass2 outer = new OuterClass2();
        outer.outerMethod();
    }
}