java - 从 hashmap 写入 txt 文件

Question

我有一个 Integer,String (K,V) 的 hashMap 并且只想将字符串值写入文件(而不是键 Integer)并且我只想将一些第 n 个条目(无特定顺序)写入文件而不是整个 map 。我试过很多次环顾四周，但找不到将第一个 n 条目写入文件的方法。(有一些例子，我可以将值转换为字符串数组，然后执行] 但它没有提供正确的格式我想写文件)

Answer 1

这听起来像是家庭作业。

public static void main(String[] args) throws IOException {
    // first, let's build your hashmap and populate it
    HashMap<Integer, String> map = new HashMap<Integer, String>();
    map.put(1, "Value1");
    map.put(2, "Value2");
    map.put(3, "Value3");
    map.put(4, "Value4");
    map.put(5, "Value5");

    // then, define how many records we want to print to the file
    int recordsToPrint = 3;

    FileWriter fstream;
    BufferedWriter out;

    // create your filewriter and bufferedreader
    fstream = new FileWriter("values.txt");
    out = new BufferedWriter(fstream);

    // initialize the record count
    int count = 0;

    // create your iterator for your map
    Iterator<Entry<Integer, String>> it = map.entrySet().iterator();

    // then use the iterator to loop through the map, stopping when we reach the
    // last record in the map or when we have printed enough records
    while (it.hasNext() && count < recordsToPrint) {

        // the key/value pair is stored here in pairs
        Map.Entry<Integer, String> pairs = it.next();
        System.out.println("Value is " + pairs.getValue());

        // since you only want the value, we only care about pairs.getValue(), which is written to out
        out.write(pairs.getValue() + "\n");

        // increment the record count once we have printed to the file
        count++;
    }
    // lastly, close the file and end
    out.close();
}