Seven

Posted 2021-03-24 yrswby2016

/*
有一个Map集合里面存储的是学生的姓名和年龄，内容如下
{张三丰=21, 灭绝师太=38, 柳岩=28, 刘德华=40, 老鬼=36, 王二麻子=38}
a.将里面的元素用两种遍历方式打印到控制台上
b.将老鬼的年龄改成66
c.将年龄大于24的学生姓名，存入到项目下的 temp\student.txt中
 */
public class Seven {
    public static void main(String[] args) throws IOException {
        //创建hashMap集合
        HashMap<String,Integer> hm = new HashMap<>();
        hm.put("张无忌",21);
        hm.put("赵敏", 20);
        hm.put("周芷若", 19);
        hm.put("柳岩", 28);
        hm.put("刘德华", 40);
        hm.put("金毛狮王", 48);
        hm.put("老鬼",36);
        hm.put("王二麻子",38);
        //遍历方式1：

        Set<Map.Entry<String, Integer>> entries = hm.entrySet();
        for (Map.Entry<String, Integer> entry : entries) {
            String key = entry.getKey();
            Integer value = entry.getValue();
            System.out.println(key +"="+value);
        }

        //map集合修改前的集合样式
        System.out.println("map集合修改前的遍历：");
        Set<String> keyset = hm.keySet();
        for (String key : keyset) {
            System.out.println(key+"	"+hm.get(key));
        }
        //2.将老鬼的年龄修改为66
        hm.put("老鬼",66);
        //第二种遍历方式
        System.out.println("Map集合修改后遍历：");
        Iterator<String> iterator = keyset.iterator();
        while (iterator.hasNext()){
            String key = iterator.next();
            System.out.println(key + "	" +hm.get(key));
        }
        //3.将年龄大于24的学生姓名，存入到student.txt中
        BufferedWriter bw = new BufferedWriter(new FileWriter("20190810\studnet7.txt"));
        for (String key : keyset) {
            if(hm.get(key) > 24){
                bw.write(key+"
");
                bw.newLine();
                bw.flush();
            }
        }
        bw.close();
    }
}