TreeMap与Properties

Posted 2021-06-23 koito

TreeMap的测试

向TreeMap中添加key-value，要求key必须是同一个类创建的对象
因为要按照key进行排序：自然排序、定制排序
自然排序（User类中实现了Comparable接口）：

    @Test
    public void test1(){
        TreeMap map = new TreeMap();
        User u1 = new User("Tom", 23);
        User u2 = new User("Jerry", 32);
        User u3 = new User("Jack", 20);
        User u4 = new User("Rose", 18);
        map.put(u1,98);
        map.put(u2,89);
        map.put(u3,76);
        map.put(u4,100);

        Set entrySet = map.entrySet();
        Iterator iterator1 = entrySet.iterator();
        while (iterator1.hasNext()) {
            Object o = iterator1.next();
            Map.Entry entry = (Map.Entry) o;
            System.out.println(entry.getKey() + "----->" + entry.getValue());
        }
    }

定制排序：

    @Test
    public void test2(){
        TreeMap map = new TreeMap(new Comparator() {
            @Override
            public int compare(Object o1, Object o2) {
                if (o1 instanceof User && o2 instanceof User) {
                    User u1 = (User)o1;
                    User u2 = (User)o2;
                    return Integer.compare(u1.getAge(),u2.getAge());
                }
                throw new RuntimeException("输入的类型不匹配！");
            }
        });
        User u1 = new User("Tom", 23);
        User u2 = new User("Jerry", 32);
        User u3 = new User("Jack", 20);
        User u4 = new User("Rose", 18);
        map.put(u1,98);
        map.put(u2,89);
        map.put(u3,76);
        map.put(u4,100);

        Set entrySet = map.entrySet();
        Iterator iterator1 = entrySet.iterator();
        while (iterator1.hasNext()) {
            Object o = iterator1.next();
            Map.Entry entry = (Map.Entry) o;
            System.out.println(entry.getKey() + "----->" + entry.getValue());
        }
    }

Properties的测试

Properties：常用来处理配置文件。key和value都是String类型

    public static void main(String[] args) {
        FileInputStream fis = null;
        try {
            Properties pros = new Properties();
            fis = new FileInputStream("jdbc.properties");
            pros.load(fis);//加载流对应的文件
            String name = pros.getProperty("name");
            String password = pros.getProperty("password");
            System.out.println("name = " + name + ",password = " + password);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if(fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }