关于Java中System.gc() 与System.runFinalization()

System.gc  :

告诉垃圾收集器打算进行垃圾收集,而垃圾收集器进不进行收集是不确定的。只是建议进行回收

System.runFinalization():

网上搜了一下很多人都说强制调用已经失去引用的对象的finalize方法。但是我用下边的程序测试了一下

class Chair{
	public int i;
	public static int created = 0;
	public Chair() {
		i = ++created;
	}
	@Override
	protected void finalize() throws Throwable {
		System.out.println("第" + i +"个Chair调用finalize方法");
	}
}
public class Garbage{
	public static void main(String[] args) {
		for (int i = 0; i < 47; ++i) {
			new Chair();
			//System.out.println("runfinalize");
			System.runFinalization();  
			//System.gc();
		}
	}
}

  

显然我们每次new出来的Chair都已经都已经没有引用了,但是调用System.runFinalization();这些没有引用的对象还是不调用finalize这个函数,很奇怪,然后就已知搜,然后看到的仍让是很多说的强制执行。

后来看了一下JDK里面的说明:

 Calling this method suggests that the Java Virtual Machine expend
     * effort toward running the <code>finalize</code> methods of objects
     * that have been found to be discarded but whose <code>finalize</code>
     * methods have not yet been run. When control returns from the
     * method call, the Java Virtual Machine has made a best effort to

注意是suggest that  同gc一样都是建议JVM。  所以JVM可以选择执行或者不执行

  

 

posted @ 2013-11-14 18:16  E_star  阅读(1593)  评论(1编辑  收藏