Boolean method for a class with an array...Please help!!


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Thread: Boolean method for a class with an array...Please help!!

  1. #1
    Join Date
    Nov 2005
    Posts
    44

    Boolean method for a class with an array...Please help!!

    Hi,

    I'm still new to Java, and get a bit lost sometimes implementing simple stuff.

    I am writing a class that defines an array, and needs to have two constructors, one that takes no parameters and creates an empty list, and another that takes the name of a text file as a parameter and creates a list containing the numbers listed in the text file.

    I have also added a method that adds a new number to the list at any time. However, I need a boolean method that returns 'true' if the list contains the given number and 'false' otherwise. The problem is, I'm not sure how to implement this correctly.

    Also, how do I construct a toString method that will return a string representing the numbers in the list.

    My code so far is as follows:

    package testing;

    import simplejava.SimpleReader;

    public class NumberList {

    int [] numbers;
    int arraySize, size;

    public NumberList()
    {
    int[] numbers = new int[10000];
    arraySize = 10000;
    size = 0;
    }

    public NumberList(String fileName)
    { SimpleReader file = new SimpleReader(fileName);
    size =0;
    int next = file.readInt();
    while (!file.finished())
    { size++;
    next = file.readInt();
    }

    file = new SimpleReader(fileName);
    numbers = new int[size];
    arraySize = size;
    for (int i = 0; i<size; i++)
    numbers[i] = file.readInt();
    }

    public void add(int next)
    {
    numbers[size] = next;
    size++;
    }

    }

    Any help would be appreciated!!!

  2. #2
    Join Date
    Dec 2004
    Location
    San Bernardino County, California
    Posts
    1,468
    I am going to respond only to your specific questions and not comment on the code in general.

    1. The boolean return value: your method tries to FIND a number in your array and, if it finds the number, returns TRUE otherwise returns FALSE. So, you create an indicator ( let's say private boolean flag = false; ), then implement a search of your array and, if it finds the int being searched for sets flag=true, then returns the value of flag. Your work, here, will be implementing your search.

    2. implementing your numbers.toString() - remember how to walk through your array one element at a time, and build your return string by adding the "string" value of the element to the string you are building. The primitive data types "cast themselves" to strings [actually, the compiler creates the code for you to cast an int to a string]. So, initialize your string variable, then you can use the += operator to add the numbers[i] element to the string, then return the string variable.

  3. #3
    Join Date
    Nov 2005
    Posts
    44

    re: Boolean method for a class with an array...Please help!!

    Hi,

    Thanks for your advice. I'll have to go back over my ref. notes and see where to go from here.

    How bad is the included code? I'm still getting used to programming in general, let alone Java.

    Many thanks!!

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