Check out example codes for "threadsafe singleton pattern in java". It will help you in understanding the concepts better.

Code Example 1

package com.journaldev.designpatterns;

public class ASingleton {

	private static volatile ASingleton instance;
	private static Object mutex = new Object();

	private ASingleton() {
	}

	public static ASingleton getInstance() {
		ASingleton result = instance;
		if (result == null) {
			synchronized (mutex) {
				result = instance;
				if (result == null)
					instance = result = new ASingleton();
			}
		}
		return result;
	}

}

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