利用一棵堆有序的完全二叉树模拟JAVA当中PriorityQueue的实现

 1 public class SimplePriorityQueue extends AbstractQueue{
    
    static final int MAXINUM = 10;
    
    private int[] array ;
    
    private volatile int border = -1;
    public SimplePriorityQueue(int[] array){
        this.array = array;
    }
    public int size(){
        return border+1;
    }
    public void add(int t){
      border++;
      if(size()>MAXINUM)
          throw new RuntimeException();
      if(border==0)
          array[border] = t;
      else{
          shiftUp(border,t);
      }
    }
    private void shiftUp(int border, int t) {
        while (border > 0) {
            int parent = (border - 1) >>> 1;//parentNo = (nodeNo-1)/2
            int e = array[parent];
            if (t<array[parent])//调用比较器的比较方法
                break;
            array[border] = e;
            border = parent;
        }
        array[border] = t;
    }
    public Object poll(){
        if(size()==0)
            throw new RuntimeException();
        int result = array[0];
        border--;
        if(size()!=0){
        int t = array[size()];
        shiftDonw(0,t);
        }
        return result;
    }
    private void shiftDonw(int index,int t){
        int half = size()>>>1;
        while(index<half){
            int child = (index<<1) + 1;
            int left = array[child];
            int right = child + 1;
            if(right<size() && left<array[right]){
                left = array[child = right];
            }
            if(t>left)
                break;
            array[index] = left;
            index = child;        
        }
        array[index] = t;
        
    }
    @Override
    public Object peek(){
        if(size()==0)
            throw new NullPointerException();
        return array[0];
    }
}