二叉堆实现优先级队列Java

public class PriQueue {
    private static final int DEFAULT_SIZE = 10;
    private int[] Q;
    private int qsize;
    private int top = -1;

    public PriQueue() {
        qsize = DEFAULT_SIZE;
        Q = new int[qsize];
    }

    public PriQueue(int qsize) {
        this.qsize = qsize;
        Q = new int[qsize];
    }

    public boolean isEmpty() {
        return top < 0;
    }

    public void push(int item) {
        if (top >= qsize - 1) {
            System.out.println("Queue is full");
            return;
        }
        Q[++top] = item;
        riseStack(Q, top);
    }

    public int pop() {
        if (top < 0) {
            System.out.println("Queue is empty");
            return Integer.MIN_VALUE;
        }

        int retVal = Q[0];
        Q[0] = Q[top--];
        sinkStack(Q, 0, top + 1);
        return retVal;
    }

    @Override
    public String toString() {
        if (top < 0)
            return new String("[]");

        StringBuilder strb = new StringBuilder("[");
        int i = 0;
        for (; i < top; i++) {
            strb.append(Q[i] + ",");
        }
        strb.append(Q[i] + "]");

        return strb.toString();
    }


    private void riseStack(int[] arr, int index) {
        int parent = (index - 1) / 2;
        int temp = arr[index];
        while (index != 0) {
            if (temp > arr[parent]) {
                arr[index] = arr[parent];
                index = parent;
                parent = (index - 1) / 2;
            } else
                break;
        }
        arr[index] = temp;
    }
    
    private void sinkStack(int[] arr, int index, int stackSize) {
        int left = 2 * index + 1;
        int pValue = arr[index];
        while (left < stackSize) {
            if (left + 1 < stackSize)
                left = arr[left] > arr[left + 1] ? left : left + 1;
            if (arr[left] > pValue) {
                arr[index] = arr[left];
                index = left;
                left = 2 * index + 1;
            } else
                break;
        }
        arr[index] = pValue;
    }
}