package DesignPatterns;

import java.util.ArrayList;

import java.util.List;

public class Singleton {

private final static int MAX_CAPACITY = 10_000;

public static void main(String[] args) throws InterruptedException {

List<Thread> threads = new ArrayList<>(MAX_CAPACITY);

var startTime = System.currentTimeMillis();

for (int i = 0; i < MAX_CAPACITY; i++) {

threads.add(Thread.ofVirtual().start(() -> {

SingletonInstance singletonInstance = SingletonInstance.getInstance();

}));

}

var endTime = System.currentTimeMillis();

System.out.printf("it took %dms to execute.\n", endTime - startTime);

}

}

class SingletonInstance {

private static volatile SingletonInstance singletonInstance;

private SingletonInstance() {}

public static SingletonInstance getInstance() {

if (singletonInstance == null) {

synchronized (SingletonInstance.class) {

if (singletonInstance == null) {

singletonInstance = new SingletonInstance();

}

}

}

return singletonInstance;

}

}