java.lang.StringIndexOutOfBoundsException reverse

Question

我正在编写一个代码来反转字符串中的子字符串。例如： 你好，世界 结果：olleH dlrow

public class q05 {
public static void main(String[] args) {

     System.out.println("Please enter a string: ");
     Scanner sc=new Scanner(System.in);
     String str= sc.nextLine();
     int length = 0,beginString=0,j=0,i=0;
     String reversedString=new String();

   while(length<str.length()){   //check all the string

       for(i=0;str.charAt(i)!= ' ';i++){
        j++;
       }
      String subString= str.substring(beginString, j); // create substring
      String reversedsubString=new String();  // create the blank substring
      System.out.println(subString);

      while(j>=0){    // reverse the substring

          reversedsubString=reversedsubString+subString.charAt(j);
          j--;


      }


      reversedString=reversedString+reversedsubString;
      System.out.println(reversedString);
      i++;
      length++;
      }

   System.out.println(reversedString);

}

它给出了一个错误：java.lang.StringIndexOutOfBoundsException

错误在哪里？

Answer 1

由于您没有指定效率限制，这应该有效：

public static void main(String[] args) {


    String input = "Hello world";


    StringBuilder sb = new StringBuilder();
    String[] words = input.split(" ");


    for (String word : words) {

        // Second word on
        if (sb.length() > 0) {
            sb.append(" ");
        }
        sb.append(reverse(word));
    }

    System.out.println(sb.toString());
}

public static String reverse(final String s) {
    StringBuilder sb = new StringBuilder();

    // Run from end to start
    for (int i = s.length() - 1; i >= 0; i--) {
        sb.append(s.charAt(i));
    }

    return sb.toString();
}

Answer 2

这应该适合你。

public static void main(String[] args) {
        System.out.println("Please enter a string: ");
         Scanner sc=new Scanner(System.in);
         String str= sc.nextLine();
         StringBuilder reverseWords = new StringBuilder();
         String[] words = str.split("\\s+");   // space(s) are the delimiters

         for (String word : words) { //fetch a single word from inputted sentence
             char[] charArray = word.toCharArray();
             int end = word.length() - 1;//length of word

             StringBuilder revWords = new StringBuilder();
             for (int i = end; i >= 0; i--) {//start the loop from end to get the last char from words 
                 revWords.append(charArray[ i]);//add the last char of word into stringbuilder
             }
             reverseWords.append(revWords);
             reverseWords.append(" ");     // separate the words
         }
         System.out.print(reverseWords);
        }