将用户输入添加到地图并将整数键增加 1

Question

Java 新手，刚开始做地图，尝试了几天但成功有限，（代码中的 cmets）欢迎所有建议。理想情况下，我想从一个未填充的地图开始，纯粹用用户输入 playerName 填充它，并在输入每个名称时将整数值加一。希望这符合所有准则！

/**
 * Constructor for objects of class player Creates player
 * objects and tests for unique player name
 */
public player() {
    Map<String, Integer> playerMap = new HashMap<>();
    System.out.println("Players in game: " + playerMap.isEmpty());
    playerMap.put("Fred", 1);
    playerMap.put("Bob", 2);
    playerMap.put("Alice", 3);
    playerMap.put("Charlotte", 4);
    playerMap.put("Catherine", 5);
    System.out.println("Players in game: " + playerMap.size());

    /**
     * user input via dialogue to get another playerName String
     * playerName set to Catherine for testing
     */
    String playerName = "Catherine";
    boolean existing = playerMap.containsValue(playerName);
    System.out.println(existing);
    if (existing = true) {
        int playerNumber = 5;
        /**
         * user input via dialogue to get another playerName I need
         * to set playerNumber = highest existing key in map then
         * increment by one then add values to map loop until all
         * players have been entered, I am considering while
         * (playerName != "last"); playerNumber set to 5 for
         * testing
         */
        playerNumber = playerNumber++;
        playerMap.put(playerName, playerNumber);
    }
}

Answer 1

containsValue 方法检查映射中是否已存在值。

“凯瑟琳”不是一个值。这是一把钥匙。

请改用containsKey。

或者你可能有反转的键和值。所以创建一个Map<Integer, String> 并在上面加上值。

Answer 2

你可以 iterate 代替 containsValue ，因为 containsValue 在内部遍历整个地图。

private boolean exists(String playerName){
   boolean isExists=false;
   for(Map.Entry<String, Integer> playerEntry:playerMap.entry()){
     if(playerEntry.getValue().equals(playerName){
       isExists=true;
       break;
     }
   }
   return isExists;
 }

它是 50-50，如果map 不包含它将遍历整个地图的值。如果它包含该值，它将中断循环并返回true。

然后您可以使用以下逻辑将put 转换为playerMap

private void addToMap(String playerName){
 if(playerName!=null && exists(playerName)){
   playerMap.put(playerName, ++playerNumber);
 }
}

Answer 3

您的 if 语句（existing = true）是错误的，因为单个“=”是赋值而不是比较。如果要比较两个布尔值是否相等，请使用双等号“==”进行比较。实际上，您甚至不需要检查“现有”变量是否为真，因为它已经是一个布尔值，只需用 if 语句包围变量，如果为真，它将进​​入 if 块，否则不会.当前，您的代码将始终输入 if 代码块，因为您将“现有”变量分配为 true。

正如之前的海报所提到的，您将名称用作键而不是值，因此您应该使用 containsKey() 方法而不是 containsValue()。

如果您的地图包含键“Catherine”，则以下代码仅应输入 if 块

  String playerName = "Catherine";
  boolean existing = playerMap.containsKey(playerName);
  if (existing) {
    int playerNumber = 5;
    /**
     * user input via dialogue to get another playerName I need
     * to set playerNumber = highest existing key in map then
     * increment by one then add values to map loop until all
     * players have been entered, I am considering while
     * (playerName != "last"); playerNumber set to 5 for
     * testing
     */
    playerNumber = playerNumber++;
    playerMap.put(playerName, playerNumber);
}

Answer 4

这段代码似乎已经成功了，并且列出了所有输入的玩家姓名，感谢所有帮助，只是想发布决赛，欢迎任何其他cmets！非常喜欢java....

 public player()
 {
  Map<Integer, String> playerMap = new HashMap<>();
  int playerNumber = 0;

 do
 {
  String playerName = 'user input request dialogue box' ("Please input a unique player name (5 Maximum): " + ((playerMap.size() - 10) * -1) + " Player slots left.");  
  boolean existing = playerMap.containsValue(playerName);                         
  System.out.println(existing);
  if (existing == false)
  {
    playerNumber = ++playerNumber;
    playerMap.put(playerNumber, playerName);
    System.out.println("Number of players in game: " + playerMap.size());

  }
} 
while (playerNumber < 5);


System.out.println("Players in game are:");
for (int a : playerMap.keySet())
{

  System.out.println("Player " + a + " is \"" + playerMap.get(a) + "\"" );



}

}