Обьясните кто понимает, нервов уже не хватает, я не понимаю что от меня хотят!
package com.javarush.task.task20.task2003;

import java.io.*;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/*
Знакомство с properties
*/

public class Solution {

    public static Map<String, String> runtimeStorage = new HashMap<>();
    public static Properties prop = new Properties();

    public static void save(OutputStream outputStream) throws Exception {
        prop.putAll(runtimeStorage);
//        for (Map.Entry<String, String> entry: runtimeStorage.entrySet()) {
//            prop.put(entry.getKey(), entry.getValue());
//        }
//        PrintWriter pw = new PrintWriter(outputStream, true);
        prop.save(outputStream, null);
    }

    public static void load(InputStream inputStream) throws IOException {
        prop.load(inputStream);
        for (String name: prop.stringPropertyNames()) {
            runtimeStorage.put(name, prop.getProperty(name));
        }
    }

    public static void main(String[] args) {
        String x;
//        runtimeStorage.put("123k", "123v");
//        runtimeStorage.put("345k", "123v");
//        runtimeStorage.put("467k", "123v");

        try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
             FileInputStream fis = new FileInputStream(x = reader.readLine());
             FileOutputStream fos = new FileOutputStream(x)) {
//            save(fos);
            load(fis);
        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println(runtimeStorage);
    }
}