RingList

/**
 * Created by SpyMomiji on 2017/4/27.
 */

public class RingList <T> {

    private class I {

        int count = 1;
        int fill = 0;
        V cv;
        V fv;

        void push(T obj){
            fv.value = obj;
            if(++fill >= count){
                V v = new V();
                v.next = fv.next;
                fv.next = v;
                fv = v;
                count++;
            } else {
                fv = fv.next;
            }

        }

        T shift(){
            if(fill <= 0) return null;
            T rv = cv.value;
            cv = cv.next;
            fill--;
            return rv;
        }

        void clear(){
            fill = 0;
            fv = cv;
        }

        void gc(){
            System.out.println("\t" + fill);
            System.out.println("\t" + count);
            int rp = count - fill -1;
            if( rp <= 0 ) return;

            V tv = fv;
            for (int i = 0; i < rp ; i++) {
                tv = tv.next;
            }
            fv.next = tv;
            count -= rp;

        }

    }

    private I index;

    public RingList() {
        index = new I();
        V v1 = new V();
        v1.next = v1;
        index.cv = v1;
        index.fv = v1;
    }

    private class V {
        T value = null;
        V next;
    }

    public void push(T obj){
        synchronized (index){
            index.push(obj);
        }
    }

    T shift(){
        synchronized (index){
            return index.shift();
        }
    }

    public void clear(){
        synchronized (index){
            index.clear();
        }
    }

    public int size(){
        synchronized (index){
            return index.fill;
        }
    }

    public void gc(){
        synchronized (index){
            index.gc();
        }
    }


}