1 package cn.itcast.p2.toolclass.collections.demo;

  2

  3 import java.util.ArrayList;

  4 import java.util.Collections;

  5 import java.util.Comparator;

  6 import java.util.List;

  7

  8 import cn.itcast.p2.comparator.ComparatorByLength;

  9

 10 public class CollectionsDemo {

 11

 12     public static void main(String[] args) {

 13         // TODO Auto-generated method stub

 14         /*

 15          * Collections：是集合框架的工具类。

 16          * 里面的方法都是静态的。

 17          */

 18         demo_1();

 19

 20     }

 21

 22     public static void demo_1() {

 23

 24         List<String> list = new ArrayList<String>();

 25

 26         list.add("abcde");

 27         list.add("cba");

 28         list.add("aa");

 29         list.add("zzz");

 30         list.add("nbaa");

 31         System.out.println(list);

 32

 33

 34

 35         //对list集合进行指定顺序的排序。

 36 //        Collections.sort(list);

 37 //        mySort(list);

 38 //        mySort(list, new ComparatorByLength());

 39         System.out.println(list);

 40

 41

 42     }

 43     //下面方法相当于Collections.sort(list,new ComparatorByLength);

 44     /*

 45     public static <T> void mySort(List<T> list,Comparator<? super T> comp) {

 46

 47             for (int i = 0; i < list.size()-1; i++) {

 48                 for (int j = i+1; j < list.size(); j++) {

 49                     if (comp.compare(list.get(i),list.get(j)) >0) {

 50 //                        T temp = list.get(i);

 51 //                        list.set(i, list.get(j));

 52 //                        list.set(j, temp);

 53                         Collections.swap(list, i, j);

 54                     }

 55                 }

 56             }

 57         }

 58     //介绍Collections.swap交换方法

 59     /*

 60     public static <T extends Comparable<? super T>> void mySort(List<T> list) {

 61         for (int i = 0; i < list.size()-1; i++) {

 62             for (int j = i+1; j < list.size(); j++) {

 63                 if (list.get(i).compareTo(list.get(j))> 0 ) {

 64 //                    T temp = list.get(i);

 65 //                    list.set(i, list.get(j));

 66 //                    list.set(j, temp);

 67                     Collections.swap(list, i, j);

 68                 }

 69             }

 70         }

 71     }*/

 72

 73     //相当于按自然顺序方法升序排列Collections.sort

 74     //public static <T extends Comparable<? super T>> void sort(List<T> list)

 75     /*

 76     public static <T extends Comparable<? super T>> void mySort(List<T> list) {

 77         for (int i = 0; i < list.size()-1; i++) {

 78             for (int j = i+1; j < list.size(); j++) {

 79                 if (list.get(i).compareTo(list.get(j))> 0 ) {

 80                     T temp = list.get(i);

 81                     list.set(i, list.get(j));

 82                     list.set(j, temp);

 83                 }

 84             }

 85         }

 86     }*/

 87

 88     //传入String类型的集合

 89  /*    public static void mySort(List<String> list) {

 90

 91         for (int i = 0; i < list.size()-1; i++) {

 92             for (int j = i+1; j < list.size(); j++) {

 93                 if (list.get(i).compareTo(list.get(j))> 0 ) {

 94                     String temp = list.get(i);

 95                     list.set(i, list.get(j));

 96                     list.set(j, temp);

 97                 }

 98             }

 99         }

100     }*/

101

102 }

 1 package cn.itcast.p2.comparator;

 2

 3 import java.util.Comparator;

 4

 5 public class ComparatorByLength implements Comparator<String> {

 6

 7     @Override

 8     public int compare(String o1, String o2) {

 9         // TODO Auto-generated method stub

10         int temp = o1.length()-o2.length();

11

12         return temp==0?o1.compareTo(o2):temp;

13     }

14

15 }