数组
升序：Arrays.sort(arr);
降序：
方法一：Arrays.sort(arr,Collections.reverseOrder());
方法二：
package com.yh.sort;import java.util.Arrays;import parator;public class SortOverride {public static void main(String[] args) {// TODO Auto-generated method stubInteger[] arr = { 4, 6, 3, 9, 1, 5, 8 };Comparator<Integer> c = new Mycomparator(); // 实例化一个Comparator对象Arrays.sort(arr, c);for (Integer ele : arr) {System.out.print(ele + " ");}}}class Mycomparator implements Comparator<Integer> {@Overridepublic int compare(Integer o1, Integer o2) {if(o1 > o2)return -1;if(o1 < o2)return 1;return 0;}}
ArrayList
升序：Collections.sort(arr);
降序：Collections.sort(arr,Collections.reverseOrder());
注：reverse()是倒序
String str = "qwewq";
String str1 =new StringBuilder(str).reverse().toString();
