Heap + build heap, insert, delete, sort + java implementation

package testpackage;

import java.util.Arrays;

public class Heap {
        //建立大顶堆
        public static void buildMaxHeap(int[] a) {
            for(int i=(a.length/2)-1;i>=0;i--) {
                adjustDown(a,i,a.length);
            }
        }
        // adjust down 
        public  static  void adjustDown( int [] a, int i, int len) {
             int temp,j;
            temp = a[i];
             for (j=2*i+1;j<len;j=2*j+1) {        // j is the child node of the current i, the default is the left node 
                if (j+1< len&&a[j+1]>a[j])        // If the right node is large, select the right node 
                    j++ ;
                 if (a[j]<=temp)                  // If the child nodes are smaller than the initial value temp, it means that the position has been found 
                    break ;
                 else {                           
                    a[i] =a[j];                    // If there is no termination, then adjust the large value in the child node to i at     
                    i=j;                        // At the same time, i drops to the position of j 
                }
            }
            a[i] = temp;                            // put temp in the final position 
        }
         // heap sort 
        public  static  void heapSort( int [] a) {
            buildMaxHeap(a);
            for(int i=a.length-1;i>=0;i--) {
                int temp=a[0];
                a[0]=a[i];
                a[i]=temp;
                adjustDown(a, 0,i);   // Adjust the remaining len-1 to a large top heap, loop, so use i to represent 
            }
        }
        // float up 
        public  static  void adjustUp( int [] a, int i) {
             int temp,j;
            temp=a[i];
            j=(i-1)/2;
            while(j>=0&&a[j]<temp) {
                a[i]=a[j];
                i=j;
                j = (j-1)/2 ;
            }
            a[i]=temp;
        }
        //插入
        public static int[] insert(int[] a,int num) {
            int[] b=new int[a.length+1];
            int i,j;
            i=0;
            j=0;
            while(i<a.length) b[j++]=a[i++];
            b[a.length]=num;
            adjustUp(b,a.length);
            return b;
        }
        // Delete (there are rules when deleting, the top element of the heap will be deleted) 
        public  static  int [] delete( int [] a) {
             int temp=a[0 ];
            a[0]=a[a.length-1];
            a[a.length-1]=temp;
            adjustDown(a,0,a.length-1);
            int[] b=new int[a.length-1];
            int i,j;
            i=j=0;
            while(i<a.length-1) b[j++]=a[i++];
            return b;
            
        }
        public static void main(String[] args) {
            int[] a= {5,88,45,37,91,26,13,66,50};
            buildMaxHeap(a);       //建堆
            System.out.println(Arrays.toString(a));
            a=insert(a,77);           //插入
            System.out.println(Arrays.toString(a));
            a =delete(a);            // Delete, only the top element of the heap can be deleted 
            System.out.println(Arrays.toString(a));
            heapSort(a);          //排序
            System.out.println(Arrays.toString(a));
        }
}