如何使用从 Java 中的字符串获取的输入

Question

我有以下一段代码，我稍后尝试使用用户在 if/else 语句中输入的输入：

String userGuess = JOptionPane.showInputDialog("The first card is " 
    + firstCard + ". Will the next card be higher, lower or equal?");

我如何使用他们输入的单词，即此代码所在的 if/else 语句之外的"更高"、"更低"或"等于"？我需要他们回答的代码是：

if (userGuess == "higher" && nextCard > firstCard)
{
    String userGuess = JOptionPane.showInputDialog(null, "Correct! The current card is a " 
               + nextCard + ". Will the next card be higher, lower or equal?");
    correctGuesses++;
}

编辑：谢谢你的帮助，我想通了！

Answer 1

试试这段代码：

if (userGuess.equalsIgnoreCase("higher") && nextCard > firstCard)
{
    String userGuess = JOptionPane.showInputDialog(null, "Correct! The current card is a " 
           + nextCard + ". Will the next card be higher, lower or equal?");
    correctGuesses++;
}
else if (userGuess.equalsIgnoreCase("higher") && nextCard == firstCard)
{
    String userGuess = JOptionPane.showInputDialog(null, "Correct! The current card is a " 
               + nextCard + ". Will the next card be higher, lower or equal?");
    correctGuesses++;
}
else if (userGuess.equalsIgnoreCase("lower") && nextCard < firstCard)
{
    String userGuess = JOptionPane.showInputDialog(null, "Correct! The current card is a " 
               + nextCard + ". Will the next card be higher, lower or equal?");
    correctGuesses++;
}

String不是基元类型。您不能使用==而使用：

if (userGuess.equalsIgnoreCase("higher") && nextCard > firstCard)
{

看看 Oracle 关于字符串的文档。这应该会给你进一步的帮助。祝您编码愉快！

Answer 2

有两种不错的方法：

1. 更改变量的名称（使其不会与现有的 userGuess 变量冲突）并在 if 语句外部声明它。

   String nextGuess = "";
   if (userGuess.equals("higher") && nextCard > firstCard) {
       nextGuess = JOptionPane.showInputDialog(null, "Correct! The current card is a " + nextCard + ". Will the next card be higher, lower or equal?");
       correctGuesses++;
   }
   

2. 只需在每次让用户输入内容时使用相同的 userGuess 变量即可。

   if (userGuess.equals("higher") && nextCard > firstCard) {
       userGuess = JOptionPane.showInputDialog(null, "Correct! The current card is a " + nextCard + ". Will the next card be higher, lower or equal?");
       correctGuesses++;
   }
   

Answer 3

如果你在 if 语句外部声明变量userGuess，并且只在内部分配它，那么你就可以在 if 语句之外使用它。

此外，正如其他地方所述，您应该将字符串与 equals（） 进行比较，而不是 ==。