java - java中单词之间添加空格并使每个单词除了第一个小写之外

Question

我会继续告诉你，是的，这是作业。然而，我在完成它时遇到了困难，迫切需要帮助。我对 Java 也很陌生，并且仍在学习该语言。

好吧，我正在尝试编写一个程序，要求用户输入一个不带空格的句子，但让他们将每个单词的第一个字母大写。然后，程序应在单词之间添加空格，并且仅第一个单词大写，其余单词应以小写开头。我可以在单词之间插入空格，但无法将每个单词的第一个字母小写。我尝试了几种不同的方法，最新的一种给了我这个错误消息:

 Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String ind
 ex out of range: 72
    at java.lang.AbstractStringBuilder.setCharAt(Unknown Source)
    at java.lang.StringBuilder.setCharAt(Unknown Source)
    at renfroKristinCh9PC14.main(renfroKristinCh9PC14.java:45)

我正在发布我的代码，非常感谢您能给我的任何和所有帮助。谢谢。

/*
This program will ask the user to enter a sentence without whitespaces, but 
with the first letter of each word capitilized. It will then separate the words
and have only the first word of the sentence capitalized.
*/

import java.util.*;

public class renfroKristinCh9PC14
{
public static void main(String[] args)
{
    //a string variable to hold the user's input and a variable to hold the modified sentence
    String input = "";
    //variable to hold a character
    char index;

    //create an instance of the scanner class for input
    Scanner keyboard = new Scanner(System.in);

    //welcome the user and explain the program
    userWelcome();

    //get the sentence from the user
    System.out.println("\n  Please enter a sentence without spaces but with the\n");
    System.out.println("  first letter of each word capitalized.\n");
    System.out.print("  Example: BatmanIsTheBestSuperheroEver!  ");

    input = keyboard.nextLine();

    //create an instance of the StringBuilder class
    StringBuilder sentence = new StringBuilder(input);

    //add spaces between the words
    for(int i=0; i < sentence.length(); i++)
    {
        index = sentence.charAt(i);
        if(i != 0 && Character.isUpperCase(index))
        {

            sentence.setCharAt(index, Character.toLowerCase(index));
            sentence.append(' ');


        }

        sentence.append(index);

    }   


    //show the new sentence to the user
    System.out.println("\n\n  Your sentence is now: "+sentence);
}
/***********************************************************************************    *************************
************************************************************************************    *************************

This function welcomes the user and exlains the program
*/

public static void userWelcome()
{

    System.out.println("\n\n       ****************   ****************************************************\n");
    System.out.println("  *            Welcome to the Word Seperator Program                   *");
    System.out.println("  *  This application will ask you to enter a sentence without       *");
    System.out.println("  *  spaces but with each word capitalized, and will then alter the  *");
    System.out.println("  *  sentence so that there arespaces between each word and          *");
    System.out.println("  *  only the first word of the sentence is capitalized              *");
    System.out.println("\n  ********************************************************************\n");
}

}

Answer 1

您正在附加到您正在迭代的同一字符串。相反，只需将您的句子设置为空的StringBuilder即可。然后，您可以在迭代输入时附加到该内容。例如:

StringBuilder sentence = new StringBuilder();

//add spaces between the words
for(int i=0; i < input.length(); i++)
{
  char letter = input.charAt(i);
  if(i != 0 && Character.isUpperCase(letter))
  {
    sentence.append(' ');
    sentence.append(Character.toLowerCase(letter));
  }
  else
  {
    sentence.append(letter);
  }
}   

(请注意，我已将变量名称从 index 更改为 letter，这样就不会那么困惑了。)