IO流加集合加强练习题附答案(6)

public static void main(String[] args) { Map map=new TreeMap(new Comparator() { @Override

public int compare(String o1, String o2) { return o1.compareTo(o2); } });

map.put(\,\张三\); map.put(\,\李四\); map.put(\,\张武\); map.put(\,\哈哈\); map.put(\,\刘敏\); //遍历方式一

for (Entry string : map.entrySet()) {

System.out.println(\学号:\+string.getKey()+\姓名:\+string.getValue()); }

//遍历方式二

for (String string : map.keySet()) { System.out.println(\学号:\+string+\姓

名:\+map.get(string)); } } }

题目十二:用List方法,存储10个1-50(含50)的随机偶数元素,要求数字不能重复,添加完成后从大到小倒序遍历输出到控制台并使用IO流将集合中的元素按指定格式输出到当前项目的num.txt中,例如: 48,44,40,38,34,30,26......

import java.io.BufferedWriter; import java.io.FileWriter; import java.io.IOException; import java.util.ArrayList; import java.util.Random; public class Demo9 {

public static void main(String[] args) throws IOException {

// 获取随机数集合并排序

ArrayList list = getNum(); // 输出到num.txt OutputNum(list); }

private static void OutputNum(ArrayList list) throws IOException {

BufferedWriter bw = new BufferedWriter(new FileWriter(\));

for (int i = 0; i < list.size(); i++) { System.out.println(list.get(i)); if (i == list.size() - 1) { bw.write(list.get(i) + \); } else {

bw.write(list.get(i) + \); } }

bw.close(); }

public static ArrayList getNum() { ArrayList list = new ArrayList();

Random rd = new Random(); while (true) {

int num = rd.nextInt(50) + 1;

if (!list.contains(num) && num % 2 == 0) { list.add(num); }

if (list.size() == 10) { break; } }

for (int i = 0; i < list.size() - 1; i++) { for (int j = i + 1; j < list.size(); j++) { if (list.get(i) < list.get(j)) { int in = list.get(i); list.set(i, list.get(j)); list.set(j, in); } } }

return list; } }

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