即节约时间,又节约空间的单例Singleton

public class Singleton{
	private Singleton(){
		System.out.println("Singleton");
		}
		
		public static Singleton getInstance(){
			System.out.println("getInstance");
			return SingletonHolder.singleton;
			
			}
			
			
			private static class SingletonHolder{
				
				private SingletonHolder(){
					System.out.println("SingletonHolder");
					}
				private static Singleton singleton = new Singleton();
				
				}
				
				public static void  main(String[] args){
					Singleton.getInstance();
					
					}

	}