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 import java.util.TreeSet;
8
9 import cn.itcast.p2.comparator.ComparatorByLength;
10
11 public class CollectionsDemo {
12
13 public static void main(String[] args) {
14 // TODO Auto-generated method stub
15 /*
16 * Collections：是集合框架的工具类。
17 * 里面的方法都是静态的。
18 */
19 // demo_1();//排序
20 // demo_2();//折半 最值
21 // demo_3();//逆序
22 demo_4();//替换
23
24 }
25
26
27
28 private static void demo_4() {
29 // TODO Auto-generated method stub
30 List<String> list = new ArrayList<String>();
31
32 list.add("abcde");
33 list.add("cba");
34 list.add("zhangsan");
35 list.add("zhaoliu");
36 list.add("xiaoqiang");
37
38 System.out.println(list);
39 // Collections.replaceAll(list, "cba", "nba");//replaceAll相当于set(indexOf"cba","nba");
40 // Collections.fill(list, "cc");//fill一次性将集合的所有值替换或重新初始化一次
41 Collections.shuffle(list);//随机将元素安在任意位置
42 System.out.println(list);
43 }
44
45 private static void demo_3() {
46 // TODO Auto-generated method stub
47
48 // TreeSet<String> ts = new TreeSet<String>(Collections.reverseOrder());//原理就是下面这个方法
49 /* TreeSet<String> ts = new TreeSet<String>(new Comparator<String>() {
50 public int compare(String o1, String o2) {
51 int temp = o2.compareTo(o1);
52 return temp;
53 }
54 });
55 */ //自己实现
56
57 //reverseOrder(Comparator<T> cmp),将一个已有比较器逆转
58 TreeSet<String> ts = new TreeSet<String>(Collections.reverseOrder(new ComparatorByLength()));
59 ts.add("abc");
60 ts.add("hahaha");
61 ts.add("zzz");
62 ts.add("aa");
63 ts.add("cba");
64
65 System.out.println(ts);
66 }
67
68 private static void demo_2() {
69 // TODO Auto-generated method stub
70 List<String> list = new ArrayList<String>();
71
72 list.add("abcde");
73 list.add("cba");
74 list.add("aa");
75 list.add("zzz");
76 list.add("cba");
77 list.add("nbaa");
78 //折半要先排序
79 Collections.sort(list);
80 System.out.println(list);
81
82 int index = Collections.binarySearch(list, "aaa");
83
84 System.out.println("index="+index);
85
86 //获取最大值。
87 // String max = Collections.max(list);//max=zzz
88 String max = Collections.max(list,new ComparatorByLength());
89 System.out.println("max="+max);
90 }
91
92 public static void demo_1() {
93
94 List<String> list = new ArrayList<String>();
95
96 list.add("abcde");
97 list.add("cba");
98 list.add("aa");
99 list.add("zzz");
100 list.add("nbaa");
101 System.out.println(list);
102
103
104
105 //对list集合进行指定顺序的排序。
106 // Collections.sort(list);
107 // mySort(list);
108 // mySort(list, new ComparatorByLength());
109 System.out.println(list);
110
111
112 }
113 //下面方法相当于Collections.sort(list,new ComparatorByLength);
114 /*
115 public static <T> void mySort(List<T> list,Comparator<? super T> comp) {
116
117 for (int i = 0; i < list.size()-1; i++) {
118 for (int j = i+1; j < list.size(); j++) {
119 if (comp.compare(list.get(i),list.get(j)) >0) {
120 // T temp = list.get(i);
121 // list.set(i, list.get(j));
122 // list.set(j, temp);
123 Collections.swap(list, i, j);
124 }
125 }
126 }
127 }
128 //介绍Collections.swap交换方法
129 /*
130 public static <T extends Comparable<? super T>> void mySort(List<T> list) {
131 for (int i = 0; i < list.size()-1; i++) {
132 for (int j = i+1; j < list.size(); j++) {
133 if (list.get(i).compareTo(list.get(j))> 0 ) {
134 // T temp = list.get(i);
135 // list.set(i, list.get(j));
136 // list.set(j, temp);
137 Collections.swap(list, i, j);
138 }
139 }
140 }
141 }*/
142
143 //相当于按自然顺序方法升序排列Collections.sort
144 //public static <T extends Comparable<? super T>> void sort(List<T> list)
145 /*
146 public static <T extends Comparable<? super T>> void mySort(List<T> list) {
147 for (int i = 0; i < list.size()-1; i++) {
148 for (int j = i+1; j < list.size(); j++) {
149 if (list.get(i).compareTo(list.get(j))> 0 ) {
150 T temp = list.get(i);
151 list.set(i, list.get(j));
152 list.set(j, temp);
153 }
154 }
155 }
156 }*/
157
158 //传入String类型的集合
159 /* public static void mySort(List<String> list) {
160
161 for (int i = 0; i < list.size()-1; i++) {
162 for (int j = i+1; j < list.size(); j++) {
163 if (list.get(i).compareTo(list.get(j))> 0 ) {
164 String temp = list.get(i);
165 list.set(i, list.get(j));
166 list.set(j, temp);
167 }
168 }
169 }
170 }*/
171
172 }
