软引用回收的问题

WeakReference是弱引用，SoftReference是软引用
ref是强引用，指向了weakRef，weakRef对象是强可达的，weakRef指向的对象无法通过强引用和软引用reach，所以还是弱可达的，会被回收。
关于可达性和回收时间

An object is weakly reachable if it is neither strongly nor softly
reachable but can be reached by traversing a weak reference. When the

weak references to a weakly-reachable object are cleared, the object
becomes eligible for finalization.

    public static void main(String[] args) {
        WeakReference<Object> wr = new WeakReference<Object>(new Object());
        int i=0;
        Object sr2 = wr;
        while(true){
            System.out.println(i);
            if(wr.get()!=null){
                i++;
                System.out.println("wr can reach "+wr.get());
            }else{
                System.out.println("null");
                break;
            }
            System.gc();
        }
    }

测试代码，wr在i=1时即被回收了