Thread: Are you a JAVA ninja??? Then help me PLEASE!!!!

Hi there,

I've been trying to find the errors of the following code and I'm totally stuck . The program it's the usual Vowel Counter.

If no sentence is been introduced then the program outputs the following sentence:

Usage: java VowelCounter [SENTENCE]
Try `java VowelCounter --help' for more information.

If only a word is introduced then the program outputs the following sentence:

Usage: java VowelCounter [SENTENCE]
Count the number of vowels in SENTENCE.
Example: java VowelCounter The quick brown fox jumps over the lazy dog

When we introduce more than one word then program counts the number or vowels.

I get the correct sentences when no introducing a word or only one word. When I introduce more than one word then the program does not count the vowels and I get the exception message.

PLEASE!!!! HEEELP!!! If someone could just guide me thru the error, so I can try to solve it...

ORIGINAL CODE

/**
 * Class that counts the number of vowels in a sentence.
 */
public class VowelCounter {
 
/** Flag to show the help of this program. */
private static final String HELP_FLAG  = "--help";
/** How to use this program. */
private static final String USAGE_LINE = "Usage: java VowelCounter [SENTENCE]";
/** The sentence which vowels are being counted. */
private String              sentence;
 
/**
 * Constructor.
 * @param words the words of the sentence which vowels will be counted
 */
public VowelCounter(final String[] words) {
    super();
    String space;
    String phrase= "";
    char x= 0;
    while (x < words.length) {
        if (x == 0) {
            space= "";
        } else {
            space= " ";
        }
        phrase= phrase + space + words[x];
        x= x + 1;
    }
    this.sentence= phrase;
}
 
/**
 * Getter.
 * @return the sentence which vowels are being counted
 */
public String getSentence() {
    return this.sentence;
}
 
/**
 * It counts the number of characters in the sentence.
 * @param c the character to count in the sentence
 * @return the occurrences of character 'c' in the sentence (case-insensitive)
 */
public int countNumberOf(char c) {
    int occurrences= 0;
    int x= 0;
    while (x <= this.getSentence().length()) {
        if (Character.toLowerCase(x) == Character.toLowerCase(this.getSentence().charAt(x))) {
            occurrences= occurrences + 1;
        }
        x= x + 1;
    }
    return occurrences;
}
 
/**
 * Main method.
 * @param args arguments
 */
public static void main(String[] args) {
    if (args.length() < 1) {
        System.out.println(USAGE_LINE);
        System.out.println("Try `java VowelCounter --help' for more information.");
    } else if (args.length == 1 && !HELP_FLAG.equals(args[0])) {
        System.out.println(USAGE_LINE);
        System.out.println("Count the number of vowels in SENTENCE.");
        System.out.println("Example: java VowelCounter The quick brown fox jumps over the lazy dog");
    } else {
        try {
            VowelCounter vc= new VowelCounter(args[0]);
            System.out.println("The sentence '" + vc.getSentence() + "' has:");
            System.out.println(vc.countNumberOf("a") + " 'A' vowels.");
            System.out.println(vc.countNumberOf('e') + " 'E' vowels.");
            System.out.println(vc.countNumberOf('i') + " 'I' vowels.");
            System.out.println(vc.countNumberOf('o') + " 'O' vowels.");
            System.out.println(vc.countNumberOf('u') + " 'U' vowels.");
        } catch (Exception ex) {
            System.out.println("Got error '" + ex.getMessage() + "'. Check you input and try again");
        }
    }
}
 
}

MY CODE

/**
 * Class that counts the number of vowels in a sentence.
 */
public class VowelCounter {
 
/** Flag to show the help of this program. */
private static final String HELP_FLAG  = "--help";
/** How to use this program. */
private static final String USAGE_LINE = "Usage: java VowelCounter [SENTENCE]";
/** The sentence which vowels are being counted. */
private String              sentence;
 
/**
 * Constructor.
 * @param words the words of the sentence which vowels will be counted
 */
public VowelCounter(final String[] words) {
    super();
    String space;
    String phrase= "";
    int x= 0;//error
    while (x < words.length) {
        if (x == 0) {
            space= "";
        } else {
            space= " ";
        }
        phrase= phrase + space + words[x];
        x= x + 1;
 
    }
 
    this.sentence= phrase;
}
 
/**
 * Getter.
 * @return the sentence which vowels are being counted
 */
public String getSentence() {
    return this.sentence;
}
 
/**
 * It counts the number of characters in the sentence.
 * @param c the character to count in the sentence
 * @return the occurrences of character 'c' in the sentence (case-insensitive)
 */
public int countNumberOf(char c) {
    int occurrences= 0;
    int x= 0;
    while (x <= this.getSentence().length()) {
        if (Character.toLowerCase(x) == Character.toLowerCase(this.getSentence().charAt(x))) {
            occurrences= occurrences + 1;
        }
        x= x + 1;
    }
    return occurrences;
}
 
/**
 * Main method.
 * @param args arguments
 */
public static void main(String[] args) {
 
 
    if (args.length < 1) {//Error
 
 
        System.out.println(USAGE_LINE);
        System.out.println("Try `java VowelCounter --help' for more information.");
 
 
    } else if ((args.length == 1) && !(HELP_FLAG.equals(args[0]))) {//Error
 
 
        System.out.println(USAGE_LINE);
        System.out.println("Count the number of vowels in SENTENCE.");
        System.out.println("Example: java VowelCounter The quick brown fox jumps over the lazy dog");
 
    } else {
        try {
 
 
            VowelCounter vc= new VowelCounter(args);//Error
 
 
            System.out.println("The sentence '" + vc.getSentence() + "' has:");
 
 
 
 
            System.out.println(vc.countNumberOf('a') + " 'A' vowels.");//Error            
            System.out.println(vc.countNumberOf('e') + " 'E' vowels.");
            System.out.println(vc.countNumberOf('i') + " 'I' vowels.");
            System.out.println(vc.countNumberOf('o') + " 'O' vowels.");
            System.out.println(vc.countNumberOf('u') + " 'U' vowels.");    
 
        } catch (Exception ex) {
            System.out.println("Got error '" + ex.getMessage() + "'. Check you input and try again");
        }
    }
}
 
}

Originally Posted by newbie

while (x <= this.getSentence().length()) << Problem.

As indices start at 0 in Java, <= is going to go over the range of the String when you call .charAt(x).
Test for LESS THAN only.

BINGO!!!

Thank you sooooo much. That was the error.

I don't understant the reason why using "<=" will make the 'WHILE' loop go over the range of the String, when 'x' reaches the same amount as characters have the sentence, it should jump to the "RETURN OCCURRENCES, rigth?.
I do understant that using only the "LESS THAN" will do the job, since when it passes over the character number of the sentence will jump to "RETURN OCURRENCES".

Here is my code with all errors fixed.

/**
 * Class that counts the number of vowels in a sentence.
 * @author OOPD teaching staff
 */
 
public class VowelCounter {//*******************************ERROR - fixed - ****************
 
/** Flag to show the help of this program. */
private static final String HELP_FLAG  = "--help";
 
/** How to use this program. */
private static final String USAGE_LINE = "Usage: java VowelCounter [SENTENCE]";
 
/** The sentence which vowels are being counted. */
private String              sentence;
 
/**
 * Constructor.
 * @param words the words of the sentence which vowels will be counted
 */
public VowelCounter(final String[] words) {
 
	super();
    String space;
    String phrase= "";
 
    int x;//***************************************ERROR - fixed - ***************************
    	x=0;
    while (x < words.length) {
        if (x == 0) {
            space= "";
        } else {
            space= " ";
        }
        phrase= phrase + space + words[x];
        x= x + 1;
    }
    this.sentence= phrase;
}
 
/**
 * Getter.
 * @return the sentence which vowels are being counted
 */
public String getSentence() {
    return this.sentence;
}
 
/**
 * It counts the number of characters in the sentence.
 * @param c the character to count in the sentence
 * @return the occurrences of character 'c' in the sentence (case-insensitive)
 */
public int countNumberOf(char c) {
 
	int occurrences= 0;
    int x= 0;
 
    while (x < this.getSentence().length()) {//**************ERROR - fixed ***************************
 
    	if (Character.toLowerCase(c) == Character.toLowerCase(this.getSentence().charAt(x))) {//******ERROR - fixed***********
            occurrences= occurrences + 1;
        }
        x= x + 1;
 
    }
    return occurrences;
}
 
/**
 * Main method.
 * @param args arguments
 */
public static void main ( String[] args ) {
 
	if (args.length < 1) {//****************ERROR - fixed -*************************
 
		System.out.println(USAGE_LINE);
        System.out.println("Try `java VowelCounter --help' for more information.");
 
	} else if ((args.length == 1) && !(HELP_FLAG.equals(args[0])))
		{
 
        System.out.println(USAGE_LINE);
        System.out.println("Count the number of vowels in SENTENCE.");
        System.out.println("Example: java VowelCounter The quick brown fox jumps over the lazy dog");
 
	} else {
        try {
 
        	VowelCounter vc= new VowelCounter(args);//*****************ERROR - fixed ******************
 
        	System.out.println("The sentence '" + vc.getSentence() + "' has:");
 
 
 
            System.out.println(vc.countNumberOf('a') + " 'A' vowels.");//****************ERROR - fixed ***************
 
            System.out.println(vc.countNumberOf('e') + " 'E' vowels.");
            System.out.println(vc.countNumberOf('i') + " 'I' vowels.");
            System.out.println(vc.countNumberOf('o') + " 'O' vowels.");
            System.out.println(vc.countNumberOf('u') + " 'U' vowels.");
 
        } catch (Exception ex) {
 
        	System.out.println("Got error '" + ex.getMessage() + "'. Check you input and try again");
        }
    }
}
 
}

Hi Norm,

I was getting the following error:

The sentence 'In English, nouns must be preceded by an article.' has:
Got error 'String index out of range: 49'. Check you input and try again

As newie suggest it, the issue was the "<=" from the "while" loop.

Thank you so much for the explanation.