反转字符串

Question

以下程序应该这样做：

当用户输入： The quick brown fox. Jumps over. The lazy dog.
它应输出：God yzal eth. Revo spmuj. Xof nworb kciuq eht.

但是当用户输入时：The quick brown fox. Jumps over. The lazy dog.
它输出：xof nworb kciuq ehT. revo spmuJ . god yzal ehT .

所以这是我的代码：

import java.util.*;
public class Reverse {
public static void main( String args[] ) {
    String paragraph;
    Scanner input = new Scanner (System.in);

    System.out.print("Enter a paragraph: ");
    paragraph = input.nextLine();
    paragraph = paragraph.trim();
    StringTokenizer tokens = new StringTokenizer(paragraph, ".");
    while (tokens.hasMoreTokens()){
        String ss = tokens.nextToken();
        for (int i = ss.length() - 1; i>=0; i--) {
            System.out.print(ss.charAt(i));
        }
        System.out.print(". ");
    }
    System.out.println();
}
}

我也想到了这个：

import java.util.*;

public class Reverse{

    public static void main(String[] args) {
    String paragraph;
    Scanner input = new Scanner (System.in);

    System.out.print("Enter a paragraph: ");
    paragraph = input.nextLine();
    paragraph = paragraph.trim();

    StringTokenizer parWordTokenizer = null;
    StringTokenizer parDotTokenizer = null;
    int numParDotTokens = 0;
    int numParWordTokens = 0;

    parDotTokenizer = new StringTokenizer (paragraph, ".");
    parWordTokenizer = new StringTokenizer (paragraph);
    numParDotTokens = parDotTokenizer.countTokens();
    numParWordTokens = parWordTokenizer.countTokens();

    String[] sentences = new String[numParDotTokens];
    String[] words = new String[numParWordTokens];
    String[] characters = new String[5];

    for (int i=0; i<numParDotTokens; i++) {
        sentences[i] = parDotTokenizer.nextToken();
        System.out.print("S: "+sentences[i]+"\n");
        parWordTokenizer = new StringTokenizer (sentences[i]);
        numParWordTokens = parWordTokenizer.countTokens();
        while (parDotTokenizer.hasMoreTokens()){
            String ss = parDotTokenizer.nextToken();
            for (int k = ss.length() - 1; k>=0; k--) {
                System.out.print(ss.charAt(k));
            }
            System.out.print(". ");
        }
        for (int j=0; j<numParWordTokens; j++) {
            words[j] = parWordTokenizer.nextToken();
            System.out.print("W: "+words[j]+"\n");
            while (parWordTokenizer.hasMoreTokens()){
                String ss = parWordTokenizer.nextToken();
                for (int k = ss.length() - 1; k>=0; k--) {
                    System.out.print(ss.charAt(k));
                }
                System.out.print(". ");
            }
        }
        }
    } } 

但 revo spmuJ . god yzal ehT . kciuq. nworb. xof. Exception in thread "main" java.util.NoSuchElementException at java.util.StringTokenizer.nextToken(Unknown Source) at ScrambleParagraph.main(Reverse.java:40) 请帮我解决。我一直在考虑正确的实现几天，但我是Java的新手，所以我不能真正做到这一点，至少现在。非常感谢你！

Answer 1

这大致是我会这样做的：

public static void main(String[] args) {

    String paragraph;
    Scanner input = new Scanner(System.in);

    System.out.print("Enter a paragraph: ");
    paragraph = input.nextLine();
    paragraph = paragraph.trim();

    String reversedParagraph = new StringBuilder(paragraph)
            .reverse().toString().toLowerCase();

    StringBuilder out = new StringBuilder();
    for (String sentence : reversedParagraph.split(" *\\.")) {
        if (!sentence.equals("")) {
            sentence += ". ";
            out.append(Character.toUpperCase(sentence.charAt(0))
                    + sentence.substring(1));
        }
    }
    System.out.println(out.toString().trim());

}

根据输入："The quick brown fox. Jumps over. The lazy dog."

这会产生："God yzal eht. Revo spmuj. Xof nworb kciuq eht."

这似乎是你要求的。

特殊成分是：StringBuilder.reverse()可以反转一个字符串，String.split(regex)可以根据正则表达式将字符串拆分成多个部分。在我颠倒之后，我用这个循环遍历段落中的每个句子。

Answer 2

这样会更加简单。

public String inverse(String str) {
    StringBuffer strBuf= new StringBuffer(str.trim());
    return strBuf.reverse().toString();         
}

Answer 3

如何用“。”分割输入。首先然后反转每个元素？

public class Reverse {

    public static void main(String[] args) {
        String input = "The quick brown fox. Jumps over. The lazy dog.";
        String[] sentences = input.split("\\.");
        StringBuilder result = new StringBuilder();
        for (int i = sentences.length - 1; i >= 0; i--) {
            String sentence = sentences[i];
            result.append(".").append(
                    new StringBuilder(sentence).reverse().toString());
        }
        System.out.println(result);
    }
}

输出：

.god yzal ehT .revo spmuJ .xof nworb kciuq ehT