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Thread: Having problems with String out of bounds errors

  1. #1
    Junior Member
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    Oct 2009
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    Default Having problems with String out of bounds errors

    Ok, well I am making a program which takes input, changes all multiple blanks into a single blank space, and creates a new line after a sentence is declared. A sentence will be declared by finding where the String has a "! . or ?" character followed by a blank space. It will also capitalize the first letter of the sentences.

    For example, if the user entered:

    this is an. example of desired?input! hurray.

    The output would be:

    This is an.
    Example of desired?input!

    So, I created a parseSentence() method to do the conversions required for me, but I keep running into an out of bounds error.

    First, here is the method:

    public String parseSentence(String sent) {
        	String temp;
        	for (int x = 0; x <= sent.length(); x ++) {
        		if ((sent.indexOf(sent.charAt(x)) + 1) != sent.length()){
        			if ((sent.charAt(x) & sent.charAt(x + 1)) == ' ') {
        				temp = sent.charAt(x + 1) + "";
        				sent = sent.replaceFirst(temp, "");
        			if (((sent.charAt(x) == '.') || (sent.charAt(x) == '!') || (sent.charAt(x) == '?')) & (sent.charAt(x + 1) == ' ')) {
        				temp = sent.charAt(x + 1) + "";
        				sent = sent.replaceFirst(temp, "\n");
        				sent = sent.replace(sent.charAt(x + 2), Character.toUpperCase(sent.charAt(x + 2)));
        	return sent;

    And this is the error after the input:

    Please enter a sentence:
    this    program    processes.     text files and creates! a  new  file?with * the       following.
    [B]Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 75
        at java.lang.String.charAt(String.java:686)
        at TextFileProcessorDemo.parseSentence(TextFileProcessorDemo.java:31)
        at TextFileProcessor.main(TextFileProcessor.java:36[/B])

    I thought it might have something to do with the loop executing towards the end of the String, and when charAt(x + 1) is trying to be found, there is nothing in that index so it would give the error. I tried to solve this by adding the first if statement, which I meant to make the loop essentially stop if the current value of x is equal to the length of the String. Though I know this would only be a partial fix for the (x + 1) parameters, and not the (x + 2) later on, but at least I was trying to make headway.

    However, that fix still didn't solve my problem.

    Any ideas?


  2. #2
    Super Moderator Json's Avatar
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    Default Re: Having problems with String out of bounds errors

    Hello, the thing is that when you are playing with the individual characters of a string you need to remember that the charAt position is a zero based index.

    Therefore this wont really work.

    x <= sent.length()

    Because you are looping up until the length of the string. Lets say we have a string with a length of 5 characters and you loop from 0 to 5 inclusively and the charAt is a zero based index, when you reach x = 5 and you try to get charAt(5) you will get a StringOutofBoundsException because there is no index 5 because the fifth character is actually in index 4.



    The string above is of length 4 but the indexes only go to 3. To fix this you need to change your loop to only loop while x is lower than the length.

    for (int x = 0; x < sent.length(); x ++) {

    Now that will solve the immediate problem, however I've also noticed somewhere in your code where you do this.

    sent.charAt(x + 1)

    This will also give you a StringOutofBoundsException if x is the last index in the string because x + 1 will be outside of the scope or bounds.

    I hope this gives you a clue on what you need to do to sort out your issues. If you still need to use the x + 1 check just do a check first to make sure that x isnt the last index.

    // Json

  3. #3
    Junior Member
    Join Date
    Oct 2009
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    Default Re: Having problems with String out of bounds errors

    Sorry for the delay, and thanks for the advice. I was able to get it to work, for the most part.

    Now I have the problem that when multiple spaces are detected within the array, it seems to leave an extra space when changing one of them to a return character. For example when I type "test. sent." (with two spaces after the first period) I want it to put:


    But instead, I'm getting:


    Here is my revised method, if anyone can help, that would be much appreciated. Thanks!

        public char[] parseSentence(char[] sent) {
        	sent[0] = Character.toUpperCase(sent[0]);
        	for (int x = 0; x < sent.length; x ++) {
        		if (x != (sent.length - 1)){
        			if (((sent[x] == '.') || (sent[x] == '!') || (sent[x] == '?')) && (sent[x + 1] == ' ')) {
        				sent[x + 1] = '\n';
    					if (sent[x + 2] == ' ')                // SEE NOTE
    						sent[x + 2] = '\u0000';     // SEE NOTE
    					sent[x + 2] = Character.toUpperCase(sent[x + 2]);
        			if ((sent[x] == ' ') && (sent[x + 1] == ' ')) {
        				sent[x] = '\u0000';
        	return sent;

    NOTE: The portion of code:

    if (sent[x + 2] == ' ')
         sent[x + 2] = '\u0000';

    is just something I threw in the try. It doesn't appear to have any effect on the program, but I was trying something at least. Thanks!

  4. #4
    Super Moderator helloworld922's Avatar
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    Default Re: Having problems with String out of bounds errors

    A simple solution is to convert to a String, then use the .trim() method.

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