Java IO流之Properties类的使用

/**
 * 使用Properties类来读取mysql.properties文件
 */
public class Properties02 {
    public static void main(String[] args) throws IOException {
        //1.创建Properties对象
        Properties properties = new Properties();
        properties.load(new FileReader("src\\mysql.properties"));
        //3.把键值对 显示到控制台
        properties.list(System.out);
        System.out.println("--------------------")
        //根据key 获取对应的值
        String pwd = properties.getProperty("pwd");
        String user = properties.getProperty("user");
        System.out.println("用户名：" + user);
        System.out.println("密码：" + pwd);
    }
}

/**
 * 使用Properties类 创建配置文件，修改配置文件内容
 */
public class Properties03 {
    public static void main(String[] args) throws IOException {
        Properties properties = new Properties();
        //创建
        //1.如果该文件没有key,就是创建
        //2.如果改文件有key,就是修改
        /*
           Properties父类就是Hashtable，底层就是Hashtable 核心方法

            public synchronized V put(K key, V value) {
        // Make sure the value is not null
        if (value == null) {
            throw new NullPointerException();
        }

        // Makes sure the key is not already in the hashtable.
        Entry<?,?> tab[] = table;
        int hash = key.hashCode();
        int index = (hash & 0x7FFFFFFF) % tab.length;
        @SuppressWarnings("unchecked")
        Entry<K,V> entry = (Entry<K,V>)tab[index];
        for(; entry != null ; entry = entry.next) {
            if ((entry.hash == hash) && entry.key.equals(key)) {
                V old = entry.value;
                entry.value = value;//如果key存在，就替换
                return old;
            }
        }

        addEntry(hash, key, value, index); //如果是新key,就添加
        return null;
    }
         */
        properties.setProperty("charset", "utf8");
        properties.setProperty("user", "汤姆");
        properties.setProperty("pwd", "888");
        //store()方法的第二个参数，表示注释
        properties.store(new FileOutputStream("src\\mysql2.properties"), "hello");
        System.out.println("保存配置文件成功！");
    }
}