单类模式

public class Singleton
{
 private Singleton(){}
 private static Singleton instance=new Singleton();
 public static Singleton getInstance()
 {
  return instance;
 }
}

public class Singleton
{
 private static Singleton intance=null;
  public static synchronized Singleton getInstance()
 {
  if(instance==null)
  {
   instance=new Singleton()
  }
  return instance;
 }
}

上面就是两种单类的模式代码!