Arrays in Java

Array Types
• c

Arrays

• How to randomly chose an element from a given array
  • use the length property of an array as the example below shows to

     public static void main(String args[]){
    	String[] daysInAweek={"monday","tuesday", "wednesday", "thursday","friday", "saturday", "sunday"};
    	int whichIndex = (int)(Math.random() *daysInAweek.length);
    	String dayOfWeek = daysInAweek[whichIndex];
    	System.out.println("dayOfWeek  "+ dayOfWeek );
    }
    

---

Initializing an array
The code below causes an error. Can you determine how to fix this error and what the error is?

	public static void main(String args[]){
		int[] myArrayOfIntegers;
		myArrayOfIntegers = new int[1];
		myArrayOfIntegers[0]  = 0;
		myArrayOfIntegers[1] = 3;
		}

CopyArray class
Adding an Element to an array using System.arraycopy.

	double[] originalArry ={1,2,3,4}; //stores original array 

	void addToArray(double[] array, double s)
	{
	   double[] tempArray = new double[array.length+1];
	   System.arraycopy(array, 0, tempArray, 0, array.length);
	   tempArray[tempArray.length - 1] = s;
	   originalArry =tempArray;
	//print out new array
	   for(double d :originalArry  )  System.out.println(d);
	   }

---

The old fashioned way : Add an element to an array via a loop. (Definitely not a recommended method for adding an element. Use arraylist or vector)

void addToArrayViaLoop(double[] array, double s)
		{
		   double[] tempArray = new double[array.length+1];
		   	for(int i =0;i<(tempArray .length-1);i++) tempArray[i] =array[i];
		   	tempArray[tempArray.length-1] = s;
		   	originalArry = tempArray;
		   	for(double d : originalArry ) System.out.println("new array elements"+d);
		}