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Thread: Helppppp!

  1. #1
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    Default Helppppp!


    I'm having difficulty with a current Java assignment. I believe if I can get it started properly (and know how the whole object, method, main thing works) I could finish the rest. The assignment is :

    Write a Java program that will create and manipulate an array of
    double values in several different ways. You will have at least
    two classes. Let's call them Mid2 and DVector. You may have more
    classes as you need (many of you will want class Prompter, since
    there will be keyboard input).

    Mid2: class containing the main method
    DVector: class that will be used in Mid2

    The program will be similar in structure to assignment 7, in that
    the main class Mid2 is a "driver" that will allow a user to create
    and manipulate an object (or objects) of class DVector.

    Here are the details of what each class should do.

    class DVector

    This class will contain an array of double (among other fields) and
    will have several different methods for manipulating that array
    (note that this will be a similar situation to your assignment 7
    class Student having an array of grades):

    public void show()
    method "show" will print out all the elements in the array in
    some nice readable fashion (show the value, and the slot number).
    You probably want to write this one first, as it will be helpful
    in determining if your other methods are working correctly as
    you write them.

    public void fill()
    method "fill" with no parameters will read double values from the
    keyboard and put them into the array. Get a value of every slot
    in the array. Do not worry about error checking the input values;
    you may assume the user will type well formed doubles.

    public boolean fill(int n)
    this version of fill will get keyboard input, reading doubles from
    the user, but it will only put values into the first "n" slots.
    Return "false" if the parameter n is too large (i.e., larger than
    the maximum number of slots in the array) and don't do any input;
    otherwise, do the keyboard input and return "true".

    public void fill(double val)
    write a second method called "fill" (overloaded method) that takes
    a single parameter of type double; this version of fill will put
    the parameter value into each array element; for example, the
    call fill(0.0) will set each array element to zero, whereas a call
    fill(7.3) will put the value 7.3 into each array element.

    public boolean add(double val)
    this method will put the parameter value into the next open slot
    in the array. You will have to check to make sure there is an open
    slot (make sure the array is not full already).

    public boolean set(int slot, double val)
    method "set" will take an integer and a double as parameters, and
    put the double value into the array slot indicated by the integer
    parameter. This method will return a boolean and you will have to
    do some simple error checking in the method. First, you must check
    the integer that is passed to make sure it can be used as a valid
    subscript... i.e., that it is 0 or greater, and it is not larger
    than the size of the array. Return true if the integer is good and
    the set can be done; return false if the integer is bad, and do not
    change any array values in that case.

    public boolean full()
    this method returns true if all array slots have values in them;
    it returns false if there is at least one empty array slot.

    public int size()
    this method returns the number of elements stored in the array

    public int max()
    this method return the total number of slots in the array, i.e.,
    maximum number of elements that could be stored

    public double sum()
    method "sum" will find the total sum of all elements in the array

    public double largest()
    method "largest" will find and return the largest value in the array.

    public int filter(double val)
    this method takes a single parameter of type double; it will compare
    each array element to the parameter value, and set an element to
    zero if the element is smaller than the parameter value; the method
    will return the count of how many elements got set to 0.0; for example,
    if 3 elements get changed, return a 3; if no elements are changed,
    return a 0.

    constructors as needed
    You know you need a constructor that takes a single integer as
    argument and uses that integer to set the size of the array that
    is created (see Mid2 discussion; this is like you did in assignment
    7 class Student to set the array length).

    class Mid2

    This class will contain the public static void main method.

    It will read one run line parameter -- an integer that will tell how
    many slots should be in the array (remember to do proper error
    checking... you may assume the user types a well-formed integer,
    but you need to make sure that integer is larger than 0).

    Once you have a good integer value from the run line parameter, you
    will create an object of class DVector and pass this integer parameter
    to the DVector constructor. This integer will tell DVector how large
    to make the array.

    Once you have the object of class DVector you will do this:

    a) enter a loop that asks the user what method he/she wants to run on
    the DVector object. You can do this in several different ways...
    print a menu of choices and let the user give an integer (like we did
    way back in an early Javascript program, the converter). You can
    designate choices by integer or string... you pick a way.

    b) When the user makes a choice, you will call the corresponding method
    on the object of class DVector (you may need to ask for more input...
    for example, if the user wants to run method "set"). Remember to
    make one of your choices "quit". Remember to also make two of your
    choices the "fill" methods so the user can re-fill the array easily
    if desired.

    c) When you run the selected method on the object, print out the results
    you get back (if there are return values). You might wish to use the
    method "show" to show what is in the array after some operations.

    -- Start with Mid2, get main running to where it accepts the
    command line parameter... start without error checking and just
    make sure you type in a correct positive integer for the run
    line argument when you test.

    -- Now create class DVector but only put one or two useful methods
    in it... like the constructor to make the array, and something
    like display, and fill(double val). With these, you will have
    an array full of values, and can see them. This will allow then
    growing the other methods.

    -- Now add the code in main that creates the object of class DVector.
    Since the compiler puts 0.0 in doubles by default, you should be
    able to call show() on the object and see the values.

    -- Now add code to allow the user to select a method to run and
    make the object run it. Obviously at this point the only
    methods you can choose are fill(double val) and display.

    -- once you have fill(double val) working, you can do the smaller
    methods like sum(), max(), size(), etc. and get a nice sense of

    -- Now add the method "fill()" to DVector... this means adding code
    for keyboard reading to that class.

    -- Add the call to fill() back in class Mid2... then test

    -- Add more methods to DVector, and more invocation choices to Mid2...
    test... grow it until you have all methods.
    Good ones at this point might be largest(), filter, etc.

    -- after you have these working, you can go back and create the
    other forms of fill, and the add method (which grows an un-full
    array one element at a time) and the set method. Since you have
    methods like show, largest, sum already, you will be able to see
    if your new methods work properly.

    -- Add error checking where input values are obtained to make the
    program robust.

    Can anyone help me?

  2. #2
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    Default Re: Helppppp!

    What do you think this is, a "Do Your Homework for You Forum"?

    Please show us what you have so far.

    And also post assignment in

    [code] assignment text [/code]

    It takes up less room on the page and is easier for users to read.

  3. #3
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    Default Re: Helppppp!

    Do you pass that array as a parameter or just have it as a date type?

  4. #4
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    Default Re: Helppppp!

    sum is easy

    public int sum()

    int sum =0;
    for (int x =0; x < array.length; x++)

    sum = sum + array[x];
    return sum;

  5. #5
    mmm.. coffee JavaPF's Avatar
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    Default Re: Helppppp!

    Hello DellHell,

    Welcome to the forums.

    As Javapenguin says, we won't help you do your home work unless you show us you have made a strong effort.

    Please post some code, even if it's bare bones and we can take it from there..
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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