charAt（）。equals（）导致“char无法解除引用” [英] charAt().equals() causes "char cannot be dereferenced"

问题描述

我正在尝试在不同的位置检查字符串是否为连字符（因为输入的内容因电话号码而异），但我一直收到错误

I am trying to check a string for hyphens at different positions (for a phone number because the input varies), but I keep getting the error

char无法解除引用

char cannot be dereferenced

代码：

do {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    System.out.print("Enter String");
    String raw = br.readLine();

    if (raw.length() < 10) {
        System.out.println("");
        System.out.println("Please input a valid phone number of at least 10 digits/letters");
        System.out.println("");
    } else {
        if (raw.charAt(3).equals('-') && raw.charAt(7).equals('-')) {
            System.out.println("2 Hyphens at 3 and 7");
        } else if (raw.charAt(3).equals('-')
                && raw.charAt(8).equals('-')) {
            System.out.println("2 Hyphens at 3 and 8");
        } else if (raw.charAt(3).equals('-')
                && raw.charAt(9).equals('-')) {
            System.out.println("2 Hyphens at 3 and 9");
        }
    }
} while (1 < 2);

推荐答案

如果你使用这样的东西，它会起作用：

If you use something like this, it will work:

  if (raw.charAt(3) == '-' && raw.charAt(7) == '-') {

      System.out.println("2 Hyphens at 3 and 7");

  } else if (raw.charAt(3) == '-' && raw.charAt(8) == '-') {

      System.out.println("2 Hyphens at 3 and 8");

  } else if (raw.charAt(3) == '-' && raw.charAt(9) == '-') {

      System.out.println("2 Hyphens at 3 and 9");

  }

问题在于 raw。 charAt（n）返回 char 而不是 String 。 equals（）方法只能用于对象。 Char是原始数据类型，没有任何方法。在字符上你应该使用像 == 或！= 这样的运算符。

The problem is that raw.charAt(n) returns a char and not a String. The equals() method can be used only on objects. Char is a primitive data type which has no methods. On chars you should use operators like == or !=.

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