Faster Synchronization Through Hash Maps

LoadTest.java

public class LoadTest {

    public static void main(String[] args) {
      // int count = 5000;
    	int count = 25000;
    	// int count = 100000;
    	// int count = 250000;
    	
    	long s = System.nanoTime();
    	for (int i = 0; i < 1000; i++) {
    		test3(count);
    	}
    	long e = System.nanoTime();
    	
    	System.out.println("RESULT: " + ((e - s) / 1000000.0));
    }
    
    public static void test1(int count) {
    	final Integer value = Integer.valueOf(1);
    	List<Integer> list = new ArrayList<Integer>(10000);
    	for (int i = 0; i < count; i++) {
    		list.add(value);
    	}
    }
    
    public static void test2(int count) {
    	final Integer value = Integer.valueOf(1);
    	List<Integer> list = Collections.synchronizedList(new ArrayList<Integer>(10000));
    	for (int i = 0; i < count; i++) {
    		list.add(value);
    	}
    }
    
    public static void test3(int count) {
    	final Integer value = Integer.valueOf(1);
    	Map<Long, List<Integer>> list = new HashMap<Long, List<Integer>>();
    	for (int i = 0; i < count; i++) {
    		Long key = Long.valueOf(Thread.currentThread().getId());
    		List<Integer> sublist = list.get(key);
    		if (sublist == null) {
    			sublist = new ArrayList<Integer>(10000);
    			synchronized (LoadTest.class) {
    				list.put(key, sublist);
    			}
    		}
    		sublist.add(value);
    	}
    }  
}