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

package com.iluwatar.lazy.loading;

/**
 * 
 * Lazy loading idiom defers object creation until needed.
 * <p>
 * This example shows different implementations of the pattern with increasing sophistication.
 * <p>
 * Additional information and lazy loading flavours are described in
 * http://martinfowler.com/eaaCatalog/lazyLoad.html
 *
 */
public class App {
  /**
   * Program entry point
   * 
   * @param args command line args
   */
  public static void main(String[] args) {

    // Simple lazy loader - not thread safe
    HolderNaive holderNaive = new HolderNaive();
    Heavy heavy = holderNaive.getHeavy();
    System.out.println("heavy=" + heavy);

    // Thread safe lazy loader, but with heavy synchronization on each access
    HolderThreadSafe holderThreadSafe = new HolderThreadSafe();
    Heavy another = holderThreadSafe.getHeavy();
    System.out.println("another=" + another);

    // The most efficient lazy loader utilizing Java 8 features
    Java8Holder java8Holder = new Java8Holder();
    Heavy next = java8Holder.getHeavy();
    System.out.println("next=" + next);
  }
}