Java优先级队列

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/**
 * Priority queue
 * */
public class PriorityQ {

    private int mSize ;
    private int[] datas;
    private int itemIndex;

    public PriorityQ (int s) {
        mSize = s;
        itemIndex = -1;
        datas = new int[mSize];

    }
    public void insert (int item) {
        if (itemIndex == mSize - 1) throw new IllegalStateException("the priority is full.");
        if (itemIndex == -1) {
            datas[++itemIndex]  = item;
        } else {
            for (int i = itemIndex; i >= 0; i--) {
                System.out.println(i + " = i   : " + datas[i]);
                if (item > datas[i]) {
                    datas[i + 1] = datas[i];
                } else {
                    datas[i + 1] = item;
                    itemIndex ++;
                    break;
                }
                datas[i] = item;
                itemIndex ++;
            }
        }
    }

    /**
     * check front
     * @return
     */
    public int peek () {
        if (itemIndex == -1) throw new IllegalStateException("the priority is empty.");
        return datas[itemIndex];
    }

    /**
     * check tail
     * @return
     */
    public int peekTail () {
        if (itemIndex == -1) throw new IllegalStateException("the priority is empty.");
        return datas[0];
    }

    /**
     * remove tail
     * @return
     */
    public int removeTail () {
        if (itemIndex == -1) throw new IllegalStateException("the priority is empty.");
        int remove = datas[0];
        for (int i = 0; i < itemIndex ; i++) {
            datas[i]  = datas[i+1];
        }
        itemIndex --;
        return remove;
    }

    /**
     * remove front
     * @return
     */
    public int remove () {
        if (itemIndex == -1) throw new IllegalStateException("the priority is empty.");
        int remove = datas[itemIndex];
        itemIndex --;
        return remove;
    }

    public int size () {
        return itemIndex + 1;
    }
}