//ArrayStuff.java

import javax.swing.*;
import java.awt.*;

public class ArrayStuff extends JApplet {
    //    public  void init () {
    public static void main(String[] argv) {

	long sum=0;
	JTextArea textarea = new JTextArea(10,60);
	textarea.setLineWrap( true );
	textarea.setFont( new Font("Courier",Font.BOLD,18) );
	JScrollPane scrollpane = new JScrollPane(textarea);

	//an array is used to conveniently store lots of data.
	//this data can be accessed many times and places in the program.
	//Array contains many "elements" or "components".
	//array has a name, a size or length, and an element type.

	// declare and construct an array of ints. 
	//each element is an int variable.
	int[] arr = new int[5];
	//array elements automatically initialized to zero.
	//indexes start at 0, go to size-1, here 4
	//there are 5 elements in this array.  5 int variables.

	arr[2] = 345;  //access element indexed by 2
	//it's an int varible, so can do int things with it.

	//  arr[5] = 34543;  //runtime error.  index out of bounds.

	//the index can be a variable (and usually is)
	int j=3;  //example
	arr[j] = 12345;
	JOptionPane.showMessageDialog(null,"element indexed by "+j+
				      " is "+arr[j]);
				      
	//array size determined at runtime:  so can be a variable
	String input;
	input = JOptionPane.showInputDialog("What size array you want?");
	int size = Integer.parseInt(input);
	int[] A = new int[size];   //lousy name but is generic

	//loop over (indexes of) elements of the array.  for loop typically used:
	for (int i=0; i<size; i++) {
	    input = JOptionPane.showInputDialog("Enter a number into element " + i);
	    A[i] = Integer.parseInt(input);
	    sum += A[i];    //add up the numbers, one by one as they are inputted
	}
	JOptionPane.showMessageDialog(null,"sum = "+sum);
	//each index, element, percentage of sum
	for (int i=0; i<size; i++) 
	    textarea.append(""+i+"\t"+A[i]+"\t"+((double)A[i]/sum)+"\n");	

	JOptionPane.showMessageDialog(null, 
				      scrollpane,
				      "Array stuff",
				      JOptionPane.PLAIN_MESSAGE);
	textarea.setText("");
	
	//assign random values to elements of the array:
	//pretend it's real data like stock prices, items sold
	input = JOptionPane.showInputDialog("Max range of random ints you want?");
	int range = Integer.parseInt(input);

	textarea.append("\nOur array of data:\n");
	//arrayname.length is the size of array
	for (int i=0; i<A.length; i++) {
	    //random int between 0 and range-1
	    A[i] = (int)(Math.random() * range);
	    textarea.append(A[i] + " ");  //display it
	}

	//some typical processing of data of the array.
	int min=Integer.MAX_VALUE,  max=Integer.MIN_VALUE;
	for (int i=0; i<A.length; i++) {
	    sum += A[i];
	    if (A[i] > max)
		max = A[i];
	    if (A[i] < min)
		min = A[i];
	}

	double average;
	average = (double)sum / size;

	textarea.append("\nSum= "+sum+
			"   Average: "+average+
			"   Min value: "+min+
			"  Max value: "+max);

	JOptionPane.showMessageDialog(null, 
				      scrollpane,
				      "Cool array stuff",
				      JOptionPane.PLAIN_MESSAGE);
    }
}
/* show: array out of bounds: constant and variable
i<=A.length   runtime error
int i=1    bug, missing one piece of data
*/