// This program contains several examples we examined to explore arrays.

import java.util.*;

public class ArraySample {
    public static void main(String[] args) {
        // this is an example of a good practice problem for arrays
        mystery();
                
        // example of an array initializer
        int[] list = {1, 7, 5, 6, 4, 14, 11};
        // we have to use Arrays.toString to properly format the output
        System.out.println("list = " + Arrays.toString(list));
        // we can pass the array as a pameter
        System.out.println("sum of list = " + sum(list));

        // this example demonstrated that primitive values passed as a
        // parameter are not changed by the method because copies of the values
        // are passed
        int a = 3;
        int b = 5;
        swap(a, b);
        System.out.println("a = " + a + ", b = " + b);

        // by contrast, arrays can be changed by methods because even though
        // the parameter is still a copy, what is being passed is a reference
        // to the object
        change(list);
        System.out.println("list = " + Arrays.toString(list));
    }
        
    // this method swaps the local copies of x and y, but not parameters passed
    // to the method
    public static void swap(int x, int y) {
        int temp = x;
        x = y;
        y = temp;
    }
        
    // change some values in an array
    public static void change(int[] list) {
        list[0] = -18;
        list[1] = -2004;
    }
        
    // find the sum of values in an array
    public static int sum(int[] list) {
        int sum = 0;
        for (int i = 0; i < list.length; i++) {
            // do something with list[i]
            // array traversal
            sum = sum + list[i];
        }
        return sum;
    }

    // practice problem: what is in the array after the loop?
    public static void mystery() {
        int[] a = {1, 7, 5, 6, 4, 14, 11};
        for (int i = 0; i < a.length - 1; i++) {
            if (a[i] > a[i + 1]) {
                a[i + 1] = a[i + 1] * 2;
            }
        }
    }
}