单例模式

package test;

public class Test {
	public static void main(String[] args) {
		for (int i = 0; i < 5; i++) {
			
			Singal singal=Singal.getInstance();
			System.out.println("-------------");
		}
		
	}
}

package test;

public class Singal {
	public Singal() {
		System.out.println("Test");
	}
	
	public static Singal getInstance(){
		System.out.println("getInstance");
		return innerClass.test;
//		return null;
	}
	static class innerClass{
		static{
			System.out.println("innerClass static");
		}
		public  static Singal test=new Singal();
	}
}

getInstance
innerClass static
Test
-------------
getInstance
-------------
getInstance
-------------
getInstance
-------------
getInstance
-------------

分析静态内部类 不是类加载的时候就被调用，而是在调用的时候才加载静态类属性，