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Thread: Sets

  1. #1
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    Default Sets

    Hi Ladies and Gents,

    I'm trying to teach myself about sets from scratch and the uses of them and I have thought of a method that could be useful.

    If I had a method called for example displayWordsInString() which takes a string argument called text.

    Could I get this method to return a set consisting of words that are in the string referenced by the argument.

    So myClass.displayWordsInString(" the train is late again ");


    should print out an array:



    [late,train,is,again,the]


    the order of print out is not really that important to me!!


    If there is a solution to this I could try out, it would really stretch my knowledge a bit , thanks again in advance to this great learning forum!!.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Sets

    Look at the String class's split method. It will help you extract the words from the string.

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    Default Re: Sets

    String [] text =  ["late" ,"train", "is", "again", "the"];
     
    text.split(",");
     
    for ( int i = 0; i < text.length; i++)
     
    {
      System.out.println(text[i]);
    }

    I get the following error
    Semantic error: line 1. Message split( java.lang.String ) not understood by class'[Ljava.lang.String;'

    Can you put me out my misery Norm and correct my code.... thanks a million.

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Sets

    Semantic error: line 1. Message split( java.lang.String ) not understood by class'[Ljava.lang.String;'
    Read the API doc for the split() method. What does it take for an argument?
    What argument did you give it in the code you posted?

    [Ljava.lang.String
    That is how the compiler refers to a String array.

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    Default Re: Sets

    split(String regex, int limit)

    These are the arguments in the API but to be honest I dont know what they mean or how to implement them.

    rGds

  6. #6
    Super Moderator Norm's Avatar
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    Default Re: Sets

    The doc doesn't quite tell how to code it
    String [] text = {"late" ,"train", "is", "again", "the"};
     
    text.split(",");
    The problem with your code is that text is not a String.
    Its an array of String. Different.

    Also the split() method returns an array which your code doesn't receive.

    This should compile:
    String[] aStrArray = text[0].split(",");
    The first element of the text array would be split into the array: aStrArray.
    To show the contents of that array:
    System.out.println("aStrArray=" + java.util.Arrays.toString(aStrArray));
    Last edited by Norm; July 17th, 2011 at 02:06 PM. Reason: Changed []s to {}s for array definition

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    Default Re: Sets

    Quote Originally Posted by av8 View Post
    split(String regex, int limit)

    These are the arguments in the API but to be honest I dont know what they mean or how to implement them.
    The 'limit' argument is optional (there is an overloaded method that takes just a regex String). The API docs try to tell you what you need to know to use the method. If you don't know what a 'regex' or 'regular expression' is, follow the link.

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    Default Re: Sets

    I have tried String [] text = {"late" ,"train", "is", "again", "the"}; with the curlys instead of []

    text.split(",");

    and still get an error do i need to use import java.util.*;

  9. #9
    Super Moderator Norm's Avatar
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    Default Re: Sets

    I tried to explain your problem in post #6. Did you have any questions about what I said there.
    Did you try the code I posted?

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    Default Re: Sets

    Yes thankyou Norm it worked A OK.

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