使用内部类创建单例模式的java实例

//兼顾饿汉式的内存浪费，也兼顾synchronized性能问题

public InnerClassSingleton{

private static class InnerHolder(){
  private static final InnerClassSingleton LAZY = new InnerClassSingleton();
}
 
private InnerClassSingleton(){
  if(InnerHolder.LAZY!=null){
    throw new RuntimeException("不允许创建多个实例！");
  }
}

public InnerClassSingleton getInstance(){
   return InnerHolder.LAZY;
} 

}