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集合嵌套

List嵌套List

public static void main(String[] args){//一个年级有许多班级，每个班级有许多学生，学生有姓名//定义班级List<String> classes1List = new ArrayList<>();classes1List.add("zhangsan");classes1List.add("lisi");classes1List.add("wangwu");List<String> classes2List = new ArrayList<>();classes2List.add("zhangsan2");classes2List.add("lisi2");classes2List.add("wangwu2");List<String> classes3List = new ArrayList<>();classes3List.add("zhangsan3");classes3List.add("lisi3");classes3List.add("wangwu3");//定义年级List<List<String>> gradeList = new ArrayList<>();gradeList.add(classes1List);gradeList.add(classes2List);gradeList.add(classes3List);//遍历gradeListfor (List<String> classes : gradeList) {for (int i = 0; i < classes.size(); i++) {System.out.println(classes.get(i));}System.out.println("--------------------");}}

List嵌套Map

public static void main(String[] args) {//先定义班级Map<String,String> classes1Map = new HashMap<>();classes1Map.put("001","zhangsan");classes1Map.put("002","lisi");classes1Map.put("003","wangwu");Map<String,String> classes2Map = new HashMap<>();classes2Map.put("001","zhangsan2");classes2Map.put("002","lisi2");classes2Map.put("003","wangwu2");Map<String,String> classes3Map = new HashMap<>();classes3Map.put("001","zhangsan3");classes3Map.put("002","lisi3");classes3Map.put("003","wangwu3");//定义年级List<Map<String,String>> gradeList = new ArrayList<>();gradeList.add(classes1Map);gradeList.add(classes2Map);gradeList.add(classes3Map);//遍历for (Map<String, String> classes : gradeList) {for (Map.Entry<String, String> entry : classes.entrySet()) {String id = entry.getKey();String name = entry.getValue();System.out.println(id + "--" + name);}System.out.println("------------------");}
}

Map嵌套Map

 public static void main(String[] args) {//先定义班级Map<String,String> classes1Map = new HashMap<>();classes1Map.put("001","zhangsan");classes1Map.put("002","lisi");classes1Map.put("003","wangwu");Map<String,String> classes2Map = new HashMap<>();classes2Map.put("001","zhangsan2");classes2Map.put("002","lisi2");classes2Map.put("003","wangwu2");Map<String,String> classes3Map = new HashMap<>();classes3Map.put("001","zhangsan3");classes3Map.put("002","lisi3");classes3Map.put("003","wangwu3");//再定义年级Map<String,Map<String,String>> gradeMap = new HashMap<>();gradeMap.put("第一个班级",classes1Map);gradeMap.put("第二个班级",classes2Map);gradeMap.put("第三个班级",classes3Map);//遍历for (String s : gradeMap.keySet()) {System.out.println("--------------");for (Map.Entry<String, String> entry : gradeMap.get(s).entrySet()) {String id = entry.getKey();String name = entry.getValue();System.out.println(s + ":" + id + "--" + name);}}}

Collections类

方法

排序 sort

乱序 shuffle

斗地主案例

需求

思路

1. 准备牌
   1. 完成数字和纸牌的映射，使用Map集合
   2. 利用list集合记录牌的编号
2. 洗牌：利用Collections.shuffle方法对其洗牌
3. 发牌：将牌的编号对3取余，剩下3张作为底牌
   1. 利用TreeSet集合保存三个人的拍编号
4. 看牌，通过TreeSet集合中牌的编号利用Map集合查看牌
   

代码

public static void main(String[] args) {//准备牌Map<Integer, String> pokerMap = new HashMap<>();List<Integer> pokerNum = new ArrayList<>();preparePoker(pokerMap, pokerNum);//洗牌Collections.shuffle(pokerNum);//System.out.println(pokerNum);//发牌TreeSet<Integer> player1 = takePoker(pokerNum,1);TreeSet<Integer> player2 = takePoker(pokerNum,2);TreeSet<Integer> player3 = takePoker(pokerNum,3);TreeSet<Integer> dp = takePoker(pokerNum,0);//        System.out.println(player1);
//        System.out.println(player2);
//        System.out.println(player3);
//        System.out.println(dp);//看牌lookPoker("zhangsan", player1, pokerMap);lookPoker("lisi", player2, pokerMap);lookPoker("wangwu", player3, pokerMap);lookPoker("底牌", dp, pokerMap);}//准备牌public static void preparePoker(Map<Integer, String> pokerMap, List<Integer> pokerNum) {String[] colors = {"♠", "♥", "♣", "♦"};String[] numbers = {"2", "A", "K", "Q", "J", "10", "9", "8", "7", "6", "5", "4", "3"};int index = 0;pokerMap.put(index, "大王");pokerNum.add(index);index++;pokerMap.put(index, "小王");pokerNum.add(index);index++;for (int i = 0; i < numbers.length; i++) {for (int j = 0; j < colors.length; j++) {pokerMap.put(index, colors[j] + numbers[i]);pokerNum.add(index);index++;}}//System.out.println(pokerMap);}//发牌public static TreeSet<Integer> takePoker(List<Integer> pokerNum,Integer id) {TreeSet<Integer> player1 = new TreeSet<>();TreeSet<Integer> player2 = new TreeSet<>();TreeSet<Integer> player3 = new TreeSet<>();TreeSet<Integer> dp = new TreeSet<>();//底牌for (int i = 0; i < pokerNum.size(); i++) {if (i > pokerNum.size() - 4) {dp.add(pokerNum.get(i));} else if (i % 3 == 0) {player1.add(pokerNum.get(i));} else if (i % 3 == 1) {player2.add(pokerNum.get(i));} else if (i % 3 == 2) {player3.add(pokerNum.get(i));}}if (id == 0){return dp;} else if (id == 1) {return player1;}else if (id == 2){return player2;} else if (id == 3) {return player3;}return new TreeSet<>();}//看牌public static void lookPoker(String name, TreeSet<Integer> player, Map<Integer, String> pokerMap) {System.out.println(name + "的牌是：");for (Integer pokerNum : player) {String poker = pokerMap.get(pokerNum);System.out.print(poker + " ");}System.out.println();}

日志框架

介绍

程序中的日志可以用来记录程序中运行过程中的信息，并可以进行永久存储

优势

• 可以将系统执行的信息选择性的记录到指定的位置(控制台，文件，数据库中)
• 可以随时以开关的形式控制是否记录日志，无需修改源代码
  

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