java-design-patterns/lazy-loading/src/main/java/com/iluwatar/lazyloading/HolderThreadSafe.java

package com.iluwatar.lazyloading;

/**
 * 
 * Same as HolderNaive but with added synchronization.
 * This implementation is thread safe, but each {@link #getHeavy()}
 * call costs additional synchronization overhead.
 *
 */
public class HolderThreadSafe {
	
	private Heavy heavy;
	
	public HolderThreadSafe() {
		System.out.println("HolderThreadSafe created");
	}

	public synchronized Heavy getHeavy() {
		if (heavy == null) {
			heavy = new Heavy();
		}
		return heavy;
	}
}