第一种：饿汉式

　　

1 class Singleton {
2  private static Singleton instance=new Singleton();
3  private Singleton(){}
4  static Singleton getInstance() {
5  return instance;
6  }
7 }

第二种：懒汉式

1 class Singleton {
2  private static Singleton instance=null;
3  private Singleton(){}
4  static Singleton getInstance() {
5  if(instance==null)
6  instance=new Singleton();
7  return instance;
8  }
9 }