how multiple threads invoke singleton object's method and work on them?

Question

I have multiple threads running which access singleton object and call its method and pass objects in it. In the method I do some calculations only on recieved object. I have he

Answer 1

    import java.util.ArrayList;
    import java.util.Collections;
    import java.util.List;

    public class MainClass {
        public final static int MAX_THREAD = 20;
        public MainClass() {
            // TODO Auto-generated constructor stub
        }

        public static void main(String[] args) {

            List singletonList = new MainClass().createSingletonObjects();
            singletonList = Collections.synchronizedList(singletonList); 

            int index = 0;
            for (int i = 0; i < MAX_THREAD; i++) {

                Thread thread1 = new Thread(new MyThread(singletonList,index), "Thread"+i);
                thread1.start();
                index++;
            if (index == singletonList.size()) {
            index = 0;  
            }

            }

        }

    public synchronized List createSingletonObjects(){
        List listSingleton = new ArrayList();
            listSingleton.add(MySingleton1.getInstance());
            listSingleton.add(MySingleton2.getInstance());
            listSingleton.add(MySingleton3.getInstance());
            listSingleton.add(MySingleton4.getInstance());
            listSingleton.add(MySingleton5.getInstance());

            return listSingleton;

        }

    }


public class MySingleton1 extends Singleton{
    private static Singleton mySingleton;
    private MySingleton1() {
        super();
        // TODO Auto-generated constructor stub
    }

    public static Singleton getInstance() {
        if (mySingleton == null) {
            mySingleton = new MySingleton1();
            return mySingleton;
        }
        return mySingleton;
    }


public class MySingleton2 extends Singleton{
    private static Singleton mySingleton;
    private MySingleton2() {
        super();
        // TODO Auto-generated constructor stub
    }

    public static Singleton getInstance() {
        if (mySingleton == null) {
            mySingleton = new MySingleton2();
            return mySingleton;
        }
        return mySingleton;
    }







}


public class MySingleton3 extends Singleton{
    private static Singleton mySingleton;
    private MySingleton3() {
        super();
        // TODO Auto-generated constructor stub
    }

    public static Singleton getInstance() {
        if (mySingleton == null) {
            mySingleton = new MySingleton3();
            return mySingleton;
        }
        return mySingleton;
    }







}


public class MySingleton4 extends Singleton{
    private static Singleton mySingleton;
    private MySingleton4() {
        super();
        // TODO Auto-generated constructor stub
    }

    public static Singleton getInstance() {
        if (mySingleton == null) {
            mySingleton = new MySingleton4();
            return mySingleton;
        }
        return mySingleton;
    }







}


public class MySingleton5 extends Singleton{
    private static Singleton mySingleton;
    private MySingleton5() {
        super();
        // TODO Auto-generated constructor stub
    }

    public static Singleton getInstance() {
        if (mySingleton == null) {
            mySingleton = new MySingleton5();
            return mySingleton;
        }
        return mySingleton;
    }







}