Arrays

The Mission
Together we are going to make a program, which can perform several elementary operations on integer arrays.

Question 1   Worker + application classes
You are to create a program which can initialize an integer array with random numbers in the interval 0 - 1000 using the Math.random() method.

Type in the Arrays class, which must resemble the following template:

public class Arrays {

  private int[] data = new int[10];

  //initializing the array
  public Arrays()
    for (int i=0; i < data.length; i++) {
      data[i] = (int)(Math.random()*1000);
    }//for
  }//Arrays()

  public int getElement(int index) {
    //fill in code to return an element from the array
    //the index for the element is passed as parameter
  }//getElement(int)

  public void setElement(int index, int value) {
    //fill in the code to set the element at the position
    //given by the first parameter (index) to the value
    //given by the second parameter (value)
  }//setElement(int, int)

  //printing indices and values of an array
  public String toString() {
    for (int i=0; i < data.length; i++) {
      System.out.print(i + ": " + data[i] + "\n");
    }//for
  }//toString()
}//Arrays

Compile.

Now create the application class, ArraysApp with the main:

public static void main(String[] args) {
  Arrays myArray = new Arrays();
  System.out.println(myArray);
}

Question 2
Now add the following code in main() before the println statement:

myArray.setElement(5, 5);
myArray.setElement(6, 8);
myArray.setElement(7, myArray.getElement(5) + getElement(6));
myArray.setElement(8, myArray.getElement(7) + getElement(6));

Run the program and see the difference in the array content.

Question 3  Find maximum
To the Arrays class add a method, findMax(), to find the maximum value in the array.
The method should resemble the following template:

public int findMax() {
  int max = data[0];
  for (int i = 1; i < data.length; i++) {
    if (data[i] > max) {
      max = data[i];
    }//if
  }//for

  return max;
}//findMax

In ArraysApp add the following statement to the main() method:
  System.out.println( "Maximum in myArray is: " + myArray.findMax() );

Question 4   Find minimum
Extend the Arrays class with a new method, findMin(), which returns the minimum value in the array.
Also use this method in ArraysApp.

Question 5  Find sum
Find the sum of all numbers in the array by adding a method findSum().
Follow the style from question 4.

Question 6  Find average
Find the average of all numbers in the array by adding a method findAverage().
Follow the style from assignment 4.

Hint: Use the findSum() method!

Question 7 Optional
In Arrays declare and construct three other int arrays named x, y and z.

x and y must hold 10 values whereas the number of values that z must hold is to be user defined; i.e. a value of the length must be read in.

x must initalized the same way as we did above.
y must be initialized with the values 0, 1, 2, ..9 (i.e. y[i] = i)
z[i] must be initialized with the value y[i] * y[i] for all index

In ArraysApp change the println statement so it prints the data in all three arrays: x, y, z
Save, Compile and run this program.

Question 8  Extra - only for the fast ones!
Here we want to calculate some numbers called Fibonacci numbers and save them in the array y.

Fibonacci numbers are defined as:

 i    y[i]   formula
---  ------ --------
 0     0     constant
 1     1     constant
 2     1     1 + 0
 3     2     1 + 1
 4     3     1 + 2
 5     5     3 + 2
 6     8     5 + 3
 7    13     8 + 5
 ...  ...    ...

As you can see a Fibonacci number at a certain point is the sum of the two previous numbers.
In Arrays add a method, findFibonacci(), where you use a loop to assign the sum of two previous elements to the elements of y - remember that you must manually initialise y[0] = 0 and y[1] = 1 !!