java - 从 map 中随机选择 n 个项目

Question

我正在尝试从 HashMap 中随机生成“n”个项目，其中“n”由用户确定。

这是我目前所拥有的:

public static void main(String []args){
    int numColors = 3;
    HashMap<String, String> map = new HashMap<String, String>();
    map.put("White","FFFFFF");
    map.put("Blank","000000");
    map.put("Red","ED0A15");
    map.put("Green","06F76C");
    map.put("Blue","0689FF");
    map.put("Sky Blue","00C2FC");
    map.put("Light Blue","08F0FC");
    map.put("Silver","C0BFC5");
    map.put("Mint","ABD3CA");
    map.put("Off White","FFEFF0");
    map.put("Purple","736FFA");
    map.put("Lavendar","DEBEEF");
    map.put("Hot Pink","F5159A");
    map.put("Pink","DB39CC");
    map.put("Light Pink","F5C2E3");
    map.put("Blush","C95FA7");
    map.put("Orange","D4361B");
    map.put("Yellow","DEF231");
    map.put("Warm White","F3E4C3");
    map.put("Turquoise","01DCA4");

    List<String> valuesList = new ArrayList<String>(map.values());
    int randomIndex = new Random().nextInt(valuesList.size());
    String randomValue = valuesList.get(randomIndex);

    System.out.printf(randomValue);
}

它为我打印 1 种随机颜色(十六进制)，这是我想要的，但是我不确定如何/使用哪个循环来从 map 中生成 3 种随机十六进制颜色。我将 numColors 声明为 3 只是为了尝试对此进行测试。

这是我最终的结果:

public static void main(String []args){
    int numColors = 3;
    HashMap<String, String> map = new HashMap<String, String>();
    map.put("White","FFFFFF");
    map.put("Blank","000000");
    map.put("Red","ED0A15");
    map.put("Green","06F76C");
    map.put("Blue","0689FF");
    map.put("Sky Blue","00C2FC");
    map.put("Light Blue","08F0FC");
    map.put("Silver","C0BFC5");
    map.put("Mint","ABD3CA");
    map.put("Off White","FFEFF0");
    map.put("Purple","736FFA");
    map.put("Lavendar","DEBEEF");
    map.put("Hot Pink","F5159A");
    map.put("Pink","DB39CC");
    map.put("Light Pink","F5C2E3");
    map.put("Blush","C95FA7");
    map.put("Orange","D4361B");
    map.put("Yellow","DEF231");
    map.put("Warm White","F3E4C3");
    map.put("Turquoise","01DCA4");

    List<String> keys = new ArrayList<String>(map.keySet());
    Random rand = new Random();
    for (int i = 0; i < numColors; i++) {
        String key = keys.get(rand.nextInt(keys.size()));
        System.out.println(map.get(key));
        }

 }

Answer 1

一个简单的解决方案是使用 Collections.shuffle(map) 随机播放整个 map 。然后迭代它并选择前 n 个元素。

当然，如果 map 很大而您只需要几个元素，这就没有意义了。

编辑:

自然地，使用这个解决方案你不会得到任何重复的条目