如何从字符串中删除一个字符

Question

我想通过扫描仪读取一个字符的索引，然后将其从字符串中删除。只有一个问题：如果 char 在字符串中出现多次，.replace() 会删除所有字符。

例如，我想从字符串“Texty text”中获取第一个“t”的索引，然后只删除那个“t”。然后我想获取第二个't'的索引，然后将其删除。

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
   String text = "Texty text";
   Scanner sc = new Scanner(System.in);
   int f = 0;
   int x = 0;
   while(f<1){
   char c = sc.next().charAt(0);
    for(int i = 0; i<text.length();i++){

      if(text.charAt(i)==c){

        System.out.println(x);
        x++;
      }
      else{
        x++;
      }

    }
  }
   System.out.println(text);
  }
}

Answer 1

你可以使用replaceFirst:

System.out.println(text.replaceFirst("t", ""));

Answer 2

您可能正在寻找类似以下的内容：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        String text = "Texty text";
        String copy = text;
        Scanner sc = new Scanner(System.in);
        while (true) {
            text = copy;
            System.out.print("Enter a character from '" + text + "': ");
            char c = sc.next().charAt(0);
            for (int i = 0; i < text.length(); i++) {
                if (Character.toUpperCase(text.charAt(i)) == Character.toUpperCase(c)) {
                    System.out.println(c + " was found at " + i);
                    text = text.substring(0, i) + "%" + text.substring(i + 1);
                    System.out.println("After replacing " + c + " with % at " + i + ": " + text);
                }
            }
        }
    }
}

示例运行：

Enter a character from 'Texty text': x
x was found at 2
After replacing x with % at 2: Te%ty text
x was found at 8
After replacing x with % at 8: Te%ty te%t
Enter a character from 'Texty text': t
t was found at 0
After replacing t with % at 0: %exty text
t was found at 3
After replacing t with % at 3: %ex%y text
t was found at 6
After replacing t with % at 6: %ex%y %ext
t was found at 9
After replacing t with % at 9: %ex%y %ex%
Enter a character from 'Texty text': 

Answer 3

尝试使用 txt.substring(x,y)

x = 通常为 0 ，但 x 是第一个开始索引 y = 这是您要删除的内容，例如对于字符串的最后一个单词，请编写以下代码： txt.substring(0, txt.length() - 1)

Answer 4

由于您要指定索引，因此您可能希望替换特定字符的第二个。这只是通过忽略它之前的那些来实现的。这将返回一个 Optional<String> 来封装结果。在适当的情况下抛出异常。

    public static void main(String[] args) {
        // Replace the first i
        Optional<String> opt = replace("This is a testi", 1, "i", "z");
        // Replace the second i (and so on).
        System.out.println(opt.get());
        opt = replace("This is a testi", 2, "i", "z");
        System.out.println(opt.get());
        opt = replace("This is a testi", 3, "i", "z");
        System.out.println(opt.get());
        opt = replace("This is a testi", 4, "i", "z");
        System.out.println(opt.get());
    }

    public static Optional<String> replace(String str, int occurrence, String find, String repl) {
        if (occurrence == 0) {
            throw new IllegalArgumentException("occurrence <= 0");
        }
        int i = -1;
        String strCopy = str;
        while (occurrence-- > 0) {
            i = str.indexOf(find, i+1);
            if (i < 0) {
                throw new IllegalStateException("insufficient occurrences of '" + find + "'");
            }
        }
        str = str.substring(0,i);
        return Optional.of(str + strCopy.substring(i).replaceFirst(find, repl));
    }