计算句子的第一个单词中的字母数

Question

I am in an introductory Java course at my university. For my assignment I have to write a program to display the number of 1 letter words in a sentence, 2 letter words in a sentence...etc. The sentence is user inputted. I am supposed to use a loop and I am not allowed to use arrays.

However for now just to start, I am just trying to find the number of letters in the first word of the sentence. What I have gives me either an incorrect letter count or an error saying that the String index is out of range.

  Scanner myScanner = new Scanner(System.in);

  int letters = 1; 

  int wordCount1 = 1; 

  System.out.print("Enter a sentence: ");
  String userInput = myScanner.nextLine();


  int space = userInput.indexOf(" "); // integer for a space character

  while (letters <= userInput.length()) {

    String firstWord = userInput.substring(0, space);
    if (firstWord.length() == 1)
      wordCount1 = 1;
    int nextSpace = space;
    userInput = userInput.substring(space);
  }
  System.out.print(wordCount1);

For example when I input "This is a sentence" it gives me "String index out of range: 4" Any help with this would be greatly appreciated.

Answer 1

Try with:

int len = userInput.split(" ")[0].length();

This will give you an array of words splitted by whitespace, then just get the first position in array and finally get the length.

Answer 2

userInput.indexOf(" ");

This gives you the length of the first word without the use of an array.

The StringIndexOutOfBoundsException is thrown because, since space is never updated, the code ends up trying to substring index 0 to 4 from a string with a length of 2 .

If userInput was printed in the while-loop, the output would be:

This is a sentence
 is a sentence
a sentence
ntence
ce

Then the StringIndexOutOfBounds is thrown.

The way I would count every word from the sentence without the use of an array would be:

Scanner in = new Scanner(System.in);

System.out.print("Enter a sentence: ");
String input = in.nextLine();
in.close();

int wordCount = 0;

while (input.length() > 0) {
    wordCount++;
    int space = input.indexOf(" ");
    if (space == -1) { //Tests if there is no space left
        break;
    }
    input = input.substring(space + 1, input.length());
}

System.out.println("The number of word entered is: " + wordCount);

Answer 3

Your problem was that you haven't been updating space and letter. See below your code with my little changes that should work fine.

Scanner myScanner = new Scanner(System.in);

      int letters = 1; 

      int wordCount1 = 1;
      String firstWord = null;

      System.out.print("Enter a sentence: ");
      String userInput = myScanner.nextLine();


      int space = -2; //= userInput.indexOf(" "); // integer for a space character

      while (letters <= userInput.length() && space != -1) {

        space = userInput.indexOf(" ");
        if (space != -1) 
            firstWord = userInput.substring(0, space);
        if (firstWord.length() == 1)
          wordCount1 = 1;
        userInput = userInput.substring(space + 1);
      }
      System.out.print(wordCount1);
}