Java 插入排序

package com;

public class Paixu {
    static boolean flag=true;
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[] a = random(50000);
        long l1 = System.currentTimeMillis();
        insertion_Sort(a);
        long l2 = System.currentTimeMillis();
        System.out.println("插入排序用时："+(l2-l1));
        check(a);
    }
    // 插入排序
    private static int[] insertion_Sort(int[] a){

    /* for (int i = 1; i < a.length; i++) {
            int temp = a[i];
            for (int j = i-1; j >= 0; j--) {
                if (a[j] > temp) {
                    a[j+1] = a[j];
                    if (j==0) {
                        a[0]=temp;
                    }
                }else {
                    a[j+1] = temp;
                    break;
                }
            }
        }*/
            
        // 优化插入排序算法
        for(int i=1;i<a.length;i++){
            int temp=a[i];
            int j;
            for(j=i-1;j>=0;j--) {
                if(a[j]>temp) {
                    a[j+1]=a[j];
                }else {
                    break;
                }
            }
            a[j+1]=temp;
        }
        
/*        int i,j;
        int n=a.length;
        for (i=1;i<n;i++)
        {
            j = i;
            int target = a[i];
            while (j>0 && target<a[j-1])
            {
                a[j] = a[j-1];
                j--;
            }
            a[j] = target;
        }*/
        System.out.println("***********************");
        return a;
    }
    public static int[] random(int num) {
        long start = System.currentTimeMillis();
        int[] a ;
        a = new int[num];
        for (int i = 0; i < num; i++) {
            int rand = (int) Math.round(Math.random()*num*100);
            a[i] = rand;
        }
        long end =System.currentTimeMillis();
        System.out.println("产生"+num+"个随机数花费时间=====>"+(end-start)+"毫秒");
        return a;
    }
    private static boolean check (int[] a) {
        for (int i = 0; i < a.length-1; i++) {
            if (a[i+1] < a[i]) {
                flag = false;
            }
        }
        System.out.println(flag);
        return flag;
    }
}