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Thread: Exercise 147

  1. #1
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    Default Exercise 147

    So here is the deal:

    The program below is intended to find the arithmetic mean of the numbers stored in the array q in two ways: once by storing the numbers in an ArrayList d, where you allow all the necessary conversions to be performed automatically; and once by storing them in an ArrayList e, where you perform all the conversions by hand. Complete the program.

    Here is what I have so far:

     
     double[] q = { 0.5, 2.4, 7.4, 2.8, -6.2 };
        ArrayList<Double> d = new ArrayList<Double>();
        ArrayList<Double> e = new ArrayList<Double>();
     
        for ( double x : q )
        {
          d.add( x );
          e.add ( new Double ( x ) );
        }
     
        double dTotal = 0.0,
               eTotal = 0.0;
     
        for (double c : d)
        {
            double a += c; 
        }
     
        for (double f : e)
        {
            double b += f;
        }
     
    return (dTotal / d.length);
    return (eTotal / e.length);


    --- Update ---

    I switched it a little bit. It still gives me the same error:

    for (double c : d)
     
    {
     
        dTotal += c; 
     
    }
     
     
     
    for (double f : e)
     
    {
     
        double eTotal += f;
     
    }
     
     
     
    System.out.print(dTotal / d.size());
     
    System.out.print(eTotal / e.size());


    --- Update ---

    Why does it still show "a / d.size?" I thought I fixed that. Whatever, it's supposed to be "dTotal / d.size()", etc.
    Last edited by ghostheadx; February 23rd, 2014 at 03:15 PM. Reason: fixing syntax


  2. #2
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    Default Re: Exercise 147

    Hi. The problem in your code:

    double eTotal += f;

    You should remove the 'double' for 'eTotal' as it has already been declared in

    double dTotal = 0.0, eTotal = 0.0;

    Here's the working code:

    double[] q = { 0.5, 2.4, 7.4, 2.8, -6.2 };
    ArrayList<Double> d = new ArrayList<Double>();
    ArrayList<Double> e = new ArrayList<Double>();
     
    for (double x : q) {
    	d.add(x);
    	e.add(new Double(x));
    }
     
    double dTotal = 0.0, eTotal = 0.0;
     
    for (double c : d) {
    	dTotal += c;
    }
     
    for (double f : e) {
    	// double eTotal += f;
    	eTotal += f;
    }
     
    System.out.println(dTotal / d.size());
    System.out.println(eTotal / e.size());

    It prints the mean as 1.3800000000000003.

  3. #3
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    Default Re: Exercise 147

    Thanks. It worked.

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