如何将标点符号从字符串的末尾移到开头？

Question

我正在尝试编写一个程序来反转字符串的顺序，甚至是标点符号。但是当我的向后字符串打印时。最后一个单词末尾的标点符号保留在单词的末尾，而不是被视为单个字符。

如何将结尾标点符号与最后一个单词分开，以便可以移动它？

例如： 当我输入：你好，我的名字是 jason！

我想要：!jason 是我的名字 Hello

相反，我得到：杰森！是我的名字你好

import java.util.*;

class Ideone
{
        public static void main(String[] args) {

        Scanner userInput = new Scanner(System.in);

        System.out.print("Enter a sentence: ");

        String input = userInput.nextLine();

        String[] sentence= input.split(" ");

        String backwards = "";

        for (int i = sentence.length - 1; i >= 0; i--) {
            backwards += sentence[i] + " ";
        }

        System.out.print(input + "\n");
        System.out.print(backwards);
        }
}

Answer 1

手动重新排列字符串很快就会变得复杂。通常最好（如果可能的话）编写你想要做的什么，而不是你想怎么做。

String input = "Hello my name is jason! Nice to meet you. What's your name?";

// this is *what* you want to do, part 1:
// split the input at each ' ', '.', '?' and '!', keep delimiter tokens
StringTokenizer st = new StringTokenizer(input, " .?!", true);
StringBuilder sb = new StringBuilder();
while(st.hasMoreTokens()) {
    String token = st.nextToken();
    // *what* you want to do, part 2:
    // add each token to the start of the string
    sb.insert(0, token);
}

String backwards = sb.toString();

System.out.print(input + "\n");
System.out.print(backwards);

输出：

Hello my name is jason! Nice to meet you. What's your name?
?name your What's .you meet to Nice !jason is name my Hello

对于下一个编写该代码的人或未来的自己来说，这将更容易理解。

这假设您要移动每个标点字符。如果您只想要输入字符串末尾的那个，则必须将其从输入中截断，重新排序，最后将其放在字符串的开头：

String punctuation = "";
String input = "Hello my name is jason! Nice to meet you. What's your name?";
System.out.print(input + "\n");
if(input.substring(input.length() -1).matches("[.!?]")) {
    punctuation = input.substring(input.length() -1);
    input = input.substring(0, input.length() -1);
}

StringTokenizer st = new StringTokenizer(input, " ", true);
StringBuilder sb = new StringBuilder();
while(st.hasMoreTokens()) {
    sb.insert(0, st.nextToken());
}
sb.insert(0, punctuation);
System.out.print(sb);

输出：

Hello my name is jason! Nice to meet you. What's your name?
?name your What's you. meet to Nice jason! is name my Hello

Answer 2

和其他答案一样，需要先把标点分开，然后重新排列单词，最后把标点放在开头。

您可以利用 String.join() 和 Collections.reverse()、String.endsWith() 来获得更简单的答案...

String input = "Hello my name is jason!";
String punctuation = "";
if (input.endsWith("?") || input.endsWith("!")) {
    punctuation = input.substring(input.length() - 1, input.length());
    input = input.substring(0, input.length() - 1);
}
List<String> words = Arrays.asList(input.split(" "));
Collections.reverse(words);
String reordered = punctuation + String.join(" ", words);
System.out.println(reordered);

Answer 3

下面的代码应该适合你

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class ReplaceSample {
    public static void main(String[] args) {
        String originalString = "TestStr?";
        String updatedString = "";
        String regex = "end\\p{Punct}+|\\p{Punct}+$";
        Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);
        Matcher matcher = pattern.matcher(originalString);
    while (matcher.find()) {
            int start = matcher.start();
            updatedString = matcher.group() + originalString.substring(0, start);<br>
        }
        System.out.println("Original -->" + originalString + "\nReplaced -->" +      updatedString);
    }
}

Answer 4

您需要按照以下步骤操作：

(1) 检查输入中的! 字符

(2) 如果输入包含!，则将其作为空输出字符串变量的前缀

(3) 如果输入不包含!，则创建空输出字符串变量

(4) 拆分输入字符串并以相反的顺序迭代（你已经这样做了）

您可以参考以下代码：

public static void main(String[] args) {
     Scanner userInput = new Scanner(System.in);
     System.out.print("Enter a sentence: ");
     String originalInput = userInput.nextLine();
     String backwards = "";
     String input = originalInput;

      //Define your punctuation chars into an array
       char[] punctuationChars = {'!', '?' , '.'};
        String backwards = "";

          //Remove ! from the input
         for(int i=0;i<punctuationChars.length;i++) {
          if(input.charAt(input.length()-1) == punctuationChars[i]) {
              input = input.substring(0, input.length()-1);
              backwards = punctuationChars[i]+"";
              break;
          }
        }

        String[] sentence= input.split(" ");


        for (int i = sentence.length - 1; i >= 0; i--) {
            backwards += sentence[i] + " ";
        }

        System.out.print(originalInput + "\n");

        System.out.print(input + "\n");
        System.out.print(backwards);
    }

Answer 5

不要用空格分隔；按单词边界分割。那么你就不需要关心标点符号甚至把空格放回去了，因为你也只是把它们颠倒了！

而且只有 1 行：

Arrays.stream(input.split("\\b"))
    .reduce((a, b) -> b + a)
    .ifPresent(System.out::println);

见live demo。