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Thread: Comparing a character to an array of strings

  1. #1
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    Default Comparing a character to an array of strings

    Hi everyone, this is my first post on this forum. I'm having trouble with a program assigned for homework. I would say that I am at a beginners level in java. Here's my code in class Bug:

    String[][] pathInfo = new String[5][25];

    ........;
    ........;

    /*
    Prints array for testing/debug use
    @return pathInfo 2D array
    */
    public void printArray(String[][] pathInfo)
    {
    for (int row = 0; row < 5; row++)
    {
    for (int column = 0; column < 25; column++)
    {
    if (pathInfo[row][column] == "*") !!!!<<<<------I think the problem lies here
    {
    System.out.print(pathInfo[row][column]);
    }
    else
    {}
    }
    }
    }

    public String[][] fillArrays(String[][] pathInfo) throws FileNotFoundException
    {
    Scanner bugPathScan = new Scanner(new File("bugpath.txt"));
    bugPathScan.useDelimiter("");
    for (int row = 0; row < pathInfo.length; row++)
    {
    for (int column = 0; column < pathInfo[row].length; column++)
    {
    pathInfo[row][column] = bugPathScan.next();
    }
    }
    return pathInfo;
    }

    It fills the array with info from a txt file. The text file contains a bunch of symbols, and looks something like this:

    ****-*--*
    *-----****
    *-----*--* <--my goal is to print only the '*' characters and skip the '-'
    ****-*--*


    How could I compare the value at the current position within the array to the "*" character? I've tried changing the array type to char[][] but I can't use the scanner to read in a char value. Any ideas? Your help is greatly appreciated


  2. #2
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    Default Re: Comparing a character to an array of strings

    .equals() not ==

    I think..

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    Hashmeer169 (December 4th, 2011)

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    Default Re: Comparing a character to an array of strings

    An extension of what ppme said:

    When comparing two string literals, it is best to use the .equals() method to compare if each char is the same, rather than the == comparison operator that will check if both objects are the same.

    However if you want to compare chars, use single quotation marks. EG
    /*
     * Precondition: c1 is a char.
     */
    if(c1 == 'a')
    {
      //Not included
    }

    For getting a specific char at an index in a String, look at the charAt method in the String API:

    String (Java Platform SE 6)
    Last edited by Tjstretch; December 4th, 2011 at 11:13 AM. Reason: Can't spell charAt *fails*

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    Hashmeer169 (December 4th, 2011)

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    Default Re: Comparing a character to an array of strings

    Thanks for the tip! Using the .equals method "if (pathInfo[row][column].equals('*'))" lets it compile but its still not printing anything. I'm not sure where the problem lies now though :/

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    Default Re: Comparing a character to an array of strings

    No problem, however string literals aren't chars.

    pathInfo[row][column] is a string, but '*' is a char, so you are comparing a String to a char, which I'm surprised compiles.

    Double quotes(") makes "*" a string, which you can use to compare to pathInfo.

  8. The Following User Says Thank You to Tjstretch For This Useful Post:

    Hashmeer169 (December 4th, 2011)

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