视频链接：16.32 Properties使用（2）_哔哩哔哩_bilibilihttps://www.bilibili.com/video/BV1Tz4y1X7H7?spm_id_from=333.788.player.switch&vd_source=b5775c3a4ea16a5306db9c7c1c1486b5&p=32

1.Properties集合

特性：

• 存储属性名和属性值；
• 属性名和属性值都是字符串类型；
• 没有泛型；
• 和流有关

2.Properties集合使用

public class PropertiesDemo01 {
    public static void main(String[] args) throws Exception {

        //1创建集合
        Properties properties = new Properties();

        //2添加元素
        properties.setProperty("username","root");
        properties.setProperty("age","20");

        //3打印集合元素
        System.out.println(properties.toString());

        //4遍历集合
        //4.1------使用keySet()遍历------(自己补齐)
        //4.2------使用entrySet()遍历------(自己补齐)
        //4.3------使用stringPropertyNames()遍历------
        Set<String> propertyNames = properties.stringPropertyNames();
        for (String propertyName : propertyNames) {
            System.out.println(propertyName + "======" + properties.getProperty(propertyName));
        }

        //5和流有关的方法
        //5.1--------list()方法-------
        PrintWriter printWriter = new PrintWriter("C:\\kkk.txt");
        properties.list(printWriter);
        printWriter.close();

        //5.2--------store()方法,实现保存-------
        FileOutputStream fos = new FileOutputStream("C:\\kkk.properties");
        properties.store(fos,"Mr zhang");
        fos.close();

        //5.3--------load()方法,实现数据加载-------
        Properties properties1 = new Properties();
        FileInputStream fis = new FileInputStream("C:\\kkk.properties");
        properties1.load(fis);
        fis.close();
        System.out.println("--------------");
        System.out.println(properties1.toString());
    }
}