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Thread: Help with one-dimensional array

  1. #1
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    Default Help with one-dimensional array

    Hey everyone, new to java here some troubles getting this down mostly step 4 i believe i have everything else correct not sure though.

    1. Create a one-dimensional array of 99 double values. Then, use a for loop to add a random number from 0 to 100 to each element in the array. For each value, use the random method of the Math class to get a double value between 0.0 and 1.0, and multiply it by 100.

    2. Use an enhanced for loop to sum the values in the array. Then, calculate the average value and print that value on the console followed by a blank line. Compile and test this class.

    3. Use the sort method of the Arrays class to sort the values in the array, and print themedian value (the 50th value) on the console followed by a blank line. Then, test this enhancement.

    4 .Print the 9th value of the array on the console and every 9th value after that. Then,test this enhancement

    import java.util.Arrays;
     
    public class ArrayTestApp
    {
        public static void main(String[] args)
        {
        double[] testArray = new double [99];
     
       //add a random number to each element in the array
        for (int i=0; i < testArray.length; i++)
        testArray[i] = 100.0*Math.random(); 
     
     
     
       //sum the values and print out the average
        double average = 0.0;
        for(int i = 0; i < testArray.length; i++)
        average += testArray[i];       
        average /= 99;   
        System.out.println("Average is: " + average);
        System.out.println();
     
       //sort the values and print the median
        Arrays.sort(testArray);
        System.out.println("Median is: " + testArray[testArray.length/2]);
        System.out.println();
     
      //print the 9th value and every 9th value after
     
     
     
        }
    }


  2. #2
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    Default Re: Help with one-dimensional array

    Hello brandon66!
    Quote Originally Posted by brandon66 View Post
    1. Create a one-dimensional array of 99 double values. Then, use a for loop to add a random number from 0 to 100 to each element in the array. For each value, use the random method of the Math class to get a double value between 0.0 and 1.0, and multiply it by 100.

    2. Use an enhanced for loop to sum the values in the array. Then, calculate the average value and print that value on the console followed by a blank line. Compile and test this class.

    3. Use the sort method of the Arrays class to sort the values in the array, and print themedian value (the 50th value) on the console followed by a blank line. Then, test this enhancement.

    4 .Print the 9th value of the array on the console and every 9th value after that. Then,test this enhancement
    For task 2, it says it needs an enhanced for loop. Check the java tutorial and an example.
    For task 4, since you know how to loop through an array what is the problem you are facing?
    You need to start from the 9th element and then print every 9th element of your array instead of starting in the first element (index 0) and then do something with the next element until the last one, like you do in the other for loops.

  3. #3
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    Default Re: Help with one-dimensional array

    so the enhanced for loop would look like this: ?

    import java.util.Arrays;
     
    public class ArrayTestApp
    {
        public static void main(String[] args)
        {
        double[] testArray = new double [99];
     
       //add a random number to each element in the array
        for (int i=0; i < testArray.length; i++)
        testArray[i] = 100.0*Math.random(); 
     
     
     
       //sum the values and print out the average
        double sum = 0.0;
        for(double a: testArray)
        {
            sum += a;
        }
          double average = sum/testArray.length; 
        System.out.println("Average is: " + average);
        System.out.println();   
     
       //sort the values and print the median
        Arrays.sort(testArray);
        System.out.println("Median is: " + testArray[testArray.length/2]);
        System.out.println();
     
      //print the 9th value and every 9th value after

  4. #4
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    Default Re: Help with one-dimensional array

    Quote Originally Posted by brandon66 View Post
    so the enhanced for loop would look like this: ?
    Yes, this is the correct syntax for the enhanced for loop.

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    Default Re: Help with one-dimensional array

    for step 4 would i create a for loop like this:?

     for(int i = 9; i < testArray.length; i++)
        {
        System.out.println(testArray[i]);
        }

  6. #6
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    Default Re: Help with one-dimensional array

    Quote Originally Posted by brandon66 View Post
    for step 4 would i create a for loop like this:?

     for(int i = 9; i < testArray.length; i++)
        {
        System.out.println(testArray[i]);
        }
    That way your loop will print every element in the array with an index >=9. This is because in each iteration it goes to the next index (i++ means that i is incremented by one in each iteration). But you want it to print every 9th element.

  7. #7
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    Default Re: Help with one-dimensional array

    Quote Originally Posted by brandon66 View Post
    for step 4 would i create a for loop like this:?

     for(int i = 9; i < testArray.length; i++)
        {
        System.out.println(testArray[i]);
        }
    To get it to print every 9th element after that, you could either check if i is divisible by 9, or increment i by 9 each time.
    Examples:
    for (int i = 9; i < testArray.length; i++) {
         if (i % 9 == 0)
              System.out.println(testArray[i]);
    }

    for (int i = 9; i < testArray.length; i = i + 9) {
         System.out.println(testArray[i]);
    }

  8. #8
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    Default Re: Help with one-dimensional array

    Thanks alot guys for the help here is the finished code

    import java.util.Arrays;
     
    public class ArrayTestApp
    {
        public static void main(String[] args)
        {
        double[] testArray = new double [99];
     
       //add a random number to each element in the array
        for (int i=0; i < testArray.length; i++)
        testArray[i] = 100.0*Math.random(); 
     
     
     
       //sum the values and print out the average
        double sum = 0.0;
        for(double a: testArray)
        {
            sum += a;
        }
          double average = sum/testArray.length; 
        System.out.println("Average is: " + average);
        System.out.println();   
     
       //sort the values and print the median
        Arrays.sort(testArray);
        System.out.println("Median is: " + testArray[testArray.length/2]);
        System.out.println();
     
      //print the 9th value and every 9th value after
       for (int i = 8; i < testArray.length; i = i + 9) {
         System.out.println("9th values: " + testArray[i]);
        }
      }
    }
    Last edited by brandon66; April 27th, 2012 at 10:40 AM. Reason: changed starting index from 9 to 8.

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