Java-->可变参数+集合操作的工具类
- 可变参数:
1 public class MethodDemo {
2 public static void main(String[] args) {
3 sum();//不传参数
4 sum(5); //一个参数
5 sum(1,2,3); //多个参数
6 sum(new int[]{5,6,4,7,8});
7 }
8 public static void sum(int...sum){
9 // 可变参数在方法内部其实就是一个数组
10 System.out.println("元素个数:" + sum.length);
11 System.out.println("元素内容:" + Arrays.toString(sum));
12 }
13 }
示例运行结果:
1 import java.util.*;
2
3 public class CollectionsDemo1 {
4 public static void main(String[] args) {
5 List<String> names = new ArrayList<>();
6 // names.add("小明");
7 // names.add("小白");
8 // names.add("小清");
9 // names.add("小楚");
10 //System.out.println("------------------");
11 //使用集合工具类可以一行添加元素
12 Collections.addAll(names,"小明","小白","小清","小楚");
13 System.out.println(names);
14
15 //打乱(List)集合顺序
16 Collections.shuffle(names);
17 System.out.println(names);
18
19 //将(List)集合按照指定规则进行排序
20 List<Integer> list = new ArrayList<>(); 21 // list.add(18);
22 // list.add(19);
23 // list.add(21);
24 // list.add(5);
25 Collections.addAll(list,10,1,12,13);
26 Collections.sort(list);
27 System.out.println(list);
28 }
29 }
示例运行结果:
自定义比较规则:
方式一:类自定义比较规则
示例运行结果:
可以看到,因为List集合是可重复的,所以保留了集合中数值相同的对象内容。
方式二:sort()方法自带的比较器对象
示例运行结果:
我们会发现,sort()方法自带的比较器对象进行比较,使用Lambda表达式简化后仅需一行代码即可完成比较操作,并且它会优先于类自定义比较规则进行执行,因此在实际的开发中会更加常用一点。
- 案例:斗地主游戏
- 需求:在启动游戏房间的时候,应该题前准备好54张牌,完成洗牌、发牌、牌排序逻辑。
分析:
- 当系统启动的同时需要准备好数据的时候,就可以使用静态代码块了;
- 洗牌就是打乱牌的顺序;
- 定义三个玩家,依次发出54张牌;
- 给玩家的牌进行排序;
- 输出每个玩家的牌数据。
牌类:
1 package com.companyName.d4_collection_test;
2
3 public class Card {
4 private String size;
5 private String color;
6 private int index; //牌真正的大小
7
8 public Card() {
9 }
10
11 public Card(String size, String color, int index) {
12 this.size = size;
13 this.color = color;
14 this.index = index;
15 }
16
17 public int getIndex() {
18 return index;
19 }
20
21 public void setIndex(int index) {
22 this.index = index;
23 }
24
25 public String getSize() {
26 return size;
27 }
28
29 public void setSize(String size) {
30 this.size = size;
31 }
32
33 public String getColor() {
34 return color;
35 }
36
37 public void setColor(String color) {
38 this.color = color;
39 }
40
41 @Override
42 public String toString() {
43 return size + color;
44 }
45 }
测试类:
1 import java.util.ArrayList;
2 import java.util.Collections;
3 import java.util.Comparator;
4 import java.util.List;
5
6 public class GemeDemo {
7 //1、做牌,定义一个静态代码块,用集合存储54张牌
8 public static List<Card> allCards = new ArrayList<>();
9 static {
10 String[] sizes = {"3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A", "2"};
11 String[] colors = {"❤", "♦", "♣", "♠"};
12 int index = 0;
13 for (String size : sizes) {
14 index ++;
15 for (String color : colors) {
16 Card card = new Card(size,color,index);
17 allCards.add(card);
18 }
19 }
20 //添加大小王
21 Card king = new Card("","大🃏",++index);
22 Card surname = new Card("","小🃏",++index);
23 Collections.addAll(allCards,king,surname);
24 System.out.println(allCards);
25 }
26 public static void main(String[] args) {
27 //打乱牌的顺序
28 Collections.shuffle(allCards);
29 System.out.println(allCards);
30 //三个玩家
31 List<Card> playerA = new ArrayList<>();
32 List<Card> playerB = new ArrayList<>();
33 List<Card> playerC = new ArrayList<>();
34 for (int i = 0; i < allCards.size() - 3; i++) {
35 switch (i % 3){
36 case 0:
37 playerA.add(allCards.get(i));
38 break;
39 case 1:
40 playerB.add(allCards.get(i));
41 break;
42 case 2:
43 playerC.add(allCards.get(i));
44 break;
45 }
46 }
47 //底牌
48 List<Card> lastThreeCards = allCards.subList(allCards.size() - 3, allCards.size());
49 //排序
50 sortCards(playerA);
51 sortCards(playerB);
52 sortCards(playerC);
53 //打印出来看看
54 System.out.println("A: " + playerA);
55 System.out.println("B:" + playerB);
56 System.out.println("C:" + playerC);
57 System.out.println(lastThreeCards);
58 }
59 //排序方法
60 public static void sortCards(List cards){
61 Collections.sort(cards, new Comparator<Card>() {
62 @Override
63 public int compare(Card o1, Card o2) {
64 return o2.getIndex() - o1.getIndex();
65 }
66 });
67 }
68 }
示例运行结果: