If Statement Modification (Using String Methods)

[danthegreat]

As you know, pig latin is a language all about vowels in the English language. hasAVowel() is a function that needs to be created to locate and return the index number of where a vowel is inside of a word.

I have been emailing my teacher here and there about this pig latin program and he strictly writes in his directions:

"Hints: You should not use a gigantic if/else compound statement or ladder in the function 'hasAVowel()' "


This is my current code for the function:

public static int hasAVowel(String word){//detects if the word has a vowel and returns location

        char letter=0;
        int index=0, num=0;
        for(int i=0; i<word.length(); i++){
            letter=word.charAt(i);
            if(letter=='a' || letter=='i' || letter=='o' || letter=='e' || letter=='u' || letter=='A' || letter=='I' || letter=='O' || letter=='E' || letter=='U'){
                index=i;
                i=word.length();
                num=1;
            }
        }
        if(num==0){
            index=-1;
        }


        return index;

}

(Just to help you understand, -1 means no vowel, 0 means vowel is first character, >0 means vowel is anywhere else in the string)

I emailed him about it and it is obviously not what he is looking for. He replies saying his suggestion is to use some string methods like length,substring,indexOf but obviously "I'm not going to tell you. That's part of the learning process for this assignment" (his exact words).

The notes I took in his class have only shown us the following methods:

.length()
.substring()
.indexOf()
.equals()
.charAt()
.compareTo()
.split()

How would it be possible to mimic the above if statement more concisely using one of these methods?

Cheers.

[Norm]

That's part of the learning process for this assignment" (his exact words).

Hint: Put all the vowels in a String

[danthegreat]

I broke my femur so I haven't been to class yet and just copied notes down from a friend but I don't really know what .IndexOf(string) does? Can anyone explain with an example what that does to strings in the first place?

Thanks.

[Fubarable]

I broke my femur so I haven't been to class yet and just copied notes down from a friend but I don't really know what .IndexOf(string) does? Can anyone explain with an example what that does to strings in the first place?

Better still, let me link you to a great resource that will allow you to read about any and all classes that are part of core Java, the Java API. Click on the link and then click on the entry for String, then search for the indexOf(...) method. It is a wonderful resource, and the sooner you start using it, the quicker you'll become a better programmer.

[Norm]

Do you have a copy of the API doc or a link to it? If not here is a link:
Java Platform SE 6

You need to learn how to find the doc for any java class.
The classes are listed in the lower left. Scroll down to the one you want and click on it and its doc will come into the right hand frame.

A way to see what a method like this does is to write a small test program, use the method and printout the results. Change the program and do it again. and so on.

[danthegreat]

Ok so I read about it and tested it out in Ecllipse to see if I understand it:

This is my sample code:

        String phrase="Test";
        String str="e";
            
System.out.print(phrase.indexOf(str));

The output is 1 which is correct. however would this mean I need to repeat this line over and over again to mimic my code above, for example:

String phrase="aeiou";        
    
            
        System.out.print(phrase.indexOf("a"));
        System.out.print(phrase.indexOf("e"));
        System.out.print(phrase.indexOf("i"));
        System.out.print(phrase.indexOf("o"));
        System.out.print(phrase.indexOf("u"));
        System.out.print(phrase.indexOf("A"));
        System.out.print(phrase.indexOf("E"));
        System.out.print(phrase.indexOf("I"));
        System.out.print(phrase.indexOf("O"));
System.out.print(phrase.indexOf("U"));

is there a way for IndexOf to scan multiple letters like:
system.out.print(phrase.indexof("aeiouAEIOU");

[Norm]

is there a way for IndexOf to

These types of questions are often answered by going to the API doc and reading.
Sometimes a method will be overloaded and be able to do lots of different things. Go see what this one has.

[danthegreat]

The only thing I see when reading is:

IndexOf(string)<same as above
IndexOf(string, int fromIndex)<allows you to start from a different index

Doesn't really say anything about searching more than one character..Any help?

[Norm]

Doesn't really say anything about searching more than one character

If it doesn't say, then it doesn't do it. Sometimes the doc can take some interpretation.
Be sure to copy the doc here and to ask if you don't understand what it is saying.

[Fubarable]

Myself, I'd loop through my String using charAt(int index), and then see if the char is contained in a constant String VARIABLES = "AEIOUaeiou". To see if VARIABLES contains the char of interest, I'd use the API to select an appropriate String method.

[danthegreat]

Ok so I tried to think about what is possible and then .compareTo came to mind...


According to the API, this is what the return value is:
the value 0 if the argument string is equal to this string; a value less than 0 if this string is lexicographically less than the string argument; and a value greater than 0 if this string is lexicographically greater than the string argument.

I don't really understand the bolded parts. Am I at least on the right track??

This is also what I have in code:

String vowels = "aeiouAEIOU";		
		for(int i=0; i<word.length(); i++){
letter=word.charAt(i);

[Norm]

What Strings are you comparing when you use compareTo?

What do you want the code you posted to do? It seems to be missing the end of the loop.

[danthegreat]

Maybe comparing the variable 'vowels' and 'letter' to see if the letter is the same as the vowel?

I want the code to detect the index of the vowel in the word.

I tried doing sample code:

String word = "Hello";		String vowels = "aeiouAEIOU";
		String letter="";
		
		for(int i=0; i<word.length(); i++){//loop through all the letters
			letter=letter+word.charAt(i);
			System.out.println(vowels.compareTo(letter));
		    System.out.println(letter);
			letter="";
		
}

output results:
25
H
-4
e
-11
l
-11
l
-14
o

Don't suppose that's right...lol can I have any other hints?

[Norm]

see if the letter is the same as the vowel?

The equals method would be more direct.

can I have any other hints?

What do you want to do?
You know how to get a single letter from a String.
Now how would you determine if that letter is a member of a set of letters?
See the hint in post#2

[Fubarable]

Here's some pseudo-code that explains the logic that I've used in this situation

Loop from i = 0 to < the length of the String
   get the ith char, c, from the String
   create a String variable, cAsString, and convert c to this String variable. (String has a valueOf method for this).
   check to see if the vowels String contains cAsString. String has a contains method (note that I highlighted this in red as a hint).
      If true, then you've found your index
   end of if block
end of for block

[pbrockway2]

@Fubarable: in this case cAsString is unnecessary as indexOf() works as a "is character in string?" check.

Post 3 reinstated (for what its worth):

You are using charAt() to "pick out" one letter at a time. And that looks OK to me.

Frankly what you are being told to find is a "trick": Can you think of some other string (not word) that you can use with indexOf() to tell if letter is a vowel?

[Fubarable]

@Fubarable: in this case cAsString is unnecessary as indexOf() works as a "is character in string?" check.

But contains doesn't, and I thought I did check this before posting.

edit: oh, I see. You're suggesting use of indexOf instead of contains and just checking that the result is > 0.

[danthegreat]

Ok so after trying to understand what I'm trying to do this is what I've come up with:

String word = "Hello";		String vowels = "aeiouAEIOU";


		
		for(int i=0; i<word.length(); i++){//loop through all the letters
			if(vowels.indexOf(word.charAt(i))!=-1){


				System.out.println(vowels.indexOf(word.charAt(i)));
				i=word.length();
			}






		
		}






		
}

This is my output:
1


if I enter "Daniel" instead of "Hello" for phrase, the output becomes a 0 which is wrong..Am I on the right track?

[Norm]

This is my output:
1

What is meaning of your output? What is the value that is printed?

[danthegreat]

that means 1 is the index of the first vowel seen which is exactly what i want it to do. however when i put daniel it outputs 0 which is the letter d