1. sort
对集合进行排序
1 public static <T extends Comparable<? super T>> void sort(List<T> list) 2 3 public static <T> void sort(List<T> list, 4 Comparator<? super T> c)
在使用List时想根据List中存储对象的某一字段进行排序，那么我们要用到Collections.sort方法对list排序，用Collections.sort方法对list排序有两种方法：
- 第一种是list中的对象实现Comparable接口；
- 第二种方法是根据Collections.sort重载方法来实现。
示例如下：
1 import java.util.ArrayList;
2 import java.util.Collections;
3 import java.util.Comparator;
4 import java.util.List;
5
6 public class SortTest {
7 public static void main(String[] args) {
8 List<String> lists = new ArrayList<String>();
9 List<A> list = new ArrayList<A>();
10 List<B> listB = new ArrayList<B>();
11 lists.add("5");
12 lists.add("2");
13 ists.add("9"); //lists中的对象String 本身含有compareTo方法，所以可以直接调用sort方法，按自然顺序排序，即升序排序
14 Collections.sort(lists);
15
16 A aa = new A();
17 a.setName("aa");
18 aa.setOrder(1);
19 A bb = new A();
20 bb.setName("bb");
21 bb.setOrder(2);
22 list.add(bb);
23 list.add(aa); //list中的对象A实现Comparable接口
24 Collections.sort(list);
25
26 B ab = new B();
27 ab.setName("ab");
28 ab.setOrder("1");
29 B ba = new B();
30 ba.setName("ba");
31 ba.setOrder("2");
32 listB.add(ba);
33 listB.add(ab); //根据Collections.sort重载方法来实现
34 Collections.sort(listB,new Comparator<B>(){
35 @Override
36 public int compare(B b1, B b2) {
37 return b1.getOrder().compareTo(b2.getOrder());
38 }
39
40 });
41
42 System.out.println(lists);
43 System.out.println(list);
44 System.out.println(listB);
45 }
46 }
47
48 class A implements Comparable<A>{
49 private String name;
50 private Integer order;
51 public String getName() {
52 return name;
53 }
54 public void setName(String name) {
55 this.name = name;
56 }
57 public Integer getOrder() {
58 return order;
59 }
60 public void setOrder(Integer order) {
61 this.order = order;
62 }
63 @Override
64 public String toString() {
65 return "name is "+name+" order is "+order;
66 }
67 @Override
68 public int compareTo(A a) {
69 return this.order.compareTo(a.getOrder());
70 }
71 }
72
73 class B{
74 private String name;
75 private String order;
76 public String getName() {
77 return name;
78 }
79 public void setName(String name) {
80 this.name = name;
81 }
82 public String getOrder() {
83 return order;
84 }
85 public void setOrder(String order) {
86 this.order = order;
87 }
88 @Override
89 public String toString() {
90 return "name is "+name+" order is "+order;
91 }
92 }
打印的结果为：
[2, 5, 9] [name is aa order is 1, name is bb order is 2] [name is ab order is 1, name is ba order is 2]
2. shuffle
对集合进行随机排序
1 public static void shuffle(List<?> list) 2 3 public static void shuffle(List<?> list, Random rnd)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 List c = new ArrayList();
4 c.add("w");
5 c.add("o");
6 c.add("r");
7 c.add("l");
8 c.add("d");
9 System.out.println(c);
10 Collections.shuffle(c);
11 System.out.println(c);
12 Collections.shuffle(c);
13 System.out.println(c);
14 }
15 }
运行结果为：[w, o, r, l, d]
[l, d, w, o, r]
[o, r, d, l, w]
3. binarySearch
查找指定集合中的元素，返回所查找元素的索引
1 public static <T> int binarySearch(List<? extends Comparable<? super T>> list, 2 T key) 3 4 public static <T> int binarySearch(List<? extends T> list, 5 T key, 6 Comparator<? super T> c)
示例:
1 public class Practice {
2 public static void main(String[] args){
3 List c = new ArrayList();
4 c.add("w");
5 c.add("o");
6 c.add("r");
7 c.add("l");
8 c.add("d");
9 System.out.println(c);
10 int m = Collections.binarySearch(c, "o");
11 System.out.println(m);
12 }
13 }
运行结果为：[w, o, r, l, d]
注意：若查找的元素不存在，示例中的n即表示该元素最有可能存在的位置的索引。
4. max
1 public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) 2 3 public static <T> T max(Collection<? extends T> coll, 4 Comparator<? super T> comp)
前者采用Collection内含自然比较法，后者采用Comparator进行比较.
5. min
1 public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) 2 3 public static <T> T min(Collection<? extends T> coll, 4 Comparator<? super T> comp)
前者采用Collection内含自然比较法，后者采用Comparator进行比较。
6. indexOfSubList
查找subList在list中首次出现位置的索引
1 public static int indexOfSubList(List<?> source, 2 List<?> target)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 List list = Arrays.asList("one two three four five six siven".split(" "));
4 System.out.println(list);
5 List subList = Arrays.asList("three four five six".split(" "));
6 System.out.println(Collections.indexOfSubList(list, subList));
7 }
8 }
运行结果为：[one, two, three, four, five, six, siven]
7. lastIndexOfSubList
使用与上例方法的使用相同，在此就不做介绍了。
8. replaceAll
替换批定元素为某元素,若要替换的值存在刚返回true,反之返回false
1 public static <T> boolean replaceAll(List<T> list, 2 T oldVal, 3 T newVal)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 List list = Arrays.asList("one two three four five six siven".split(" "));
4 System.out.println(list);
5 List subList = Arrays.asList("three four five six".split(" "));
6 System.out.println(Collections.replaceAll(list, "siven", "siven eight"));
7 System.out.println(list);
8 }
9 }
运行结果为：
[one, two, three, four, five, six, siven]
true
[one, two, three, four, five, six, siven eight]
9. reverse()
反转集合中元素的顺序
public static void reverse(List<?> list)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 List list = Arrays.asList("one two three four five six siven".split(" "));
4 System.out.println(list);
5 Collections.reverse(list);
6 System.out.println(list);
7 }
8 }
运行结果为：
[one, two, three, four, five, six, siven]
[siven, six, five, four, three, two, one]
10. rotate
集合中的元素向后移m个位置，在后面被遮盖的元素循环到前面来
1 public static void rotate(List<?> list, 2 int distance)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 List list = Arrays.asList("one two three four five six siven".split(" "));
4 System.out.println(list);
5 Collections.rotate(list, 1);
6 System.out.println(list);
7 }
8 }
运行结果为：
[one, two, three, four, five, six, siven]
[siven, one, two, three, four, five, six]
11. copy
将集合n中的元素全部复制到m中,并且覆盖相应索引的元素
1 public static <T> void copy(List<? super T> dest, 2 List<? extends T> src)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 List m = Arrays.asList("one two three four five six siven".split(" "));
4 System.out.println(m);
5 List n = Arrays.asList("我 是 复制过来的哈".split(" "));
6 System.out.println(n);
7 Collections.copy(m,n);
8 System.out.println(m);
9 }
10 }
运行结果为：[one, two, three, four, five, six, siven]
[我, 是, 复制过来的哈]
[我, 是, 复制过来的哈, four, five, six, siven]
12. swap
交换集合中指定元素索引的位置
1 public static void swap(List<?> list, 2 int i, 3 int j)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 List m = Arrays.asList("one two three four five six siven".split(" "));
4 System.out.println(m);
5 Collections.swap(m, 2, 3);
6 System.out.println(m);
7 }
8 }
运行结果为：
[one, two, three, four, five, six, siven]
[one, two, four, three, five, six, siven]
13. fill
用对象o替换集合list中的所有元素
1 public static <T> void fill(List<? super T> list, 2 T obj)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 List m = Arrays.asList("one two three four five six siven".split(" "));
4 System.out.println(m);
5 Collections.fill(m, "haha52T25xixi");
6 System.out.println(m);
7 }
8 }
运行结果为：
[one, two, three, four, five, six, siven]
[haha52T25xixi, haha52T25xixi, haha52T25xixi, haha52T25xixi, haha52T25xixi, haha52T25xixi, haha52T25xixi]
14. nCopies
返回大小为n的List，List不可改变,其中的所有引用都指向o
1 public static <T> List<T> nCopies(int n, 2 T o)
示例：
1 public class Practice {
2 public static void main(String[] args){
3 System.out.println(Collections.nCopies(5, "haha"));
4 }
5 }
运行结果为：
[haha, haha, haha, haha, haha]
参考：http://www.360doc.com/content/14/0829/10/15242507_405537400.shtml