关于JAVA垃圾回收的一些小tips

public class AliveTest {
    public static AliveTest A = null;
    public static void alive(){
        System.out.println("alive");
    }
    protected void finalize() throws Throwable {
        super.finalize();
        System.out.println("finalize");
        AliveTest.A = this;
        //System.out.println(A);
    }
    public static void main(String[] args) throws InterruptedException {
        A = new AliveTest();
        A=null;
        System.gc();
        Thread.sleep(500);
        if(A!=null){
            AliveTest.alive();
        }else{
            System.out.println("hehe");
        }
        
        A=null;
        System.gc();
        Thread.sleep(500);
        if(A!=null){
            AliveTest.alive();
        }else{
            System.out.println("aa");
        }
    }
}

Java 虚拟机在垃圾回收的时候最多只调用一次 finalize 方法；

 

public class ReferenceTest {
    public static final Map<Integer, Reference> map = new HashMap<Integer, Reference>();
    
    public static void main(String[] args) {
        for (int i = 0; i < 1000; i++) {
            map.put(i, new WeakReference(new ReferenceObject(i)));
        }
 
        int i = 0;
        for (Reference r : map.values()) {
            if (r.get() == null) {
                i++;
            }
        }
        System.out.println("被回收的对象数:" + i);
    }
 
    static class ReferenceObject {
        private int    i;
 
        private byte[] b;
 
        public ReferenceObject(int i) {
            this.i = i;
            b = new byte[1024 *10000];
        }
    }
}

弱引用马上就会被回收掉。