冒泡算法

记忆注意点：外层循环：arr.length - 1

     内存循环：arr.length - 1 - i

具体算法：

       public class MaopaoSort {
public static void main(String[] args) {
int[] arr = {8, 3, 120, 86, 34 };
for (int i = 0; i < arr.length-1; i++) {
for (int j = 0; j < arr.length-i-1; j++) {
if (arr[j] < arr[j+1]) {
int temp = arr[j];
arr[j] = arr[j+1];
arr[j+1]  = temp;
}
}
}
//倒序输出
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]);
}
//正序输出
for (int i = arr.length; i > 0 ; i--) {
System.out.println(arr[i-1]);
}


  }
}