/*
 * IntArrayEx.java
 *
 * Created on September 9, 2002, 12:00 AM
 *
 * Purpose is merely to illustrate integer arrays - everything is really in the main
 */

package simpleEx;

/**
 *
 * @author  mike
 */
public class IntArrayEx {
    
    /** Creates a new instance of IntArrayEx */
    public IntArrayEx() {
    }
    
    // static - don't need an object
    public static void showArray(int arr[]) {
        int cnt;
        for (cnt = 0; cnt < arr.length; cnt++) {
            System.out.println(arr[cnt]);
        }
    }
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        int cnt;
        // define an array of ints
        int empty[];
        //System.out.println("empty array");
        //showArray(empty);  // compiler stops
        //empty[0] = 3;   // invalid - array doesn't exist - compiler catches
        // define an array of 5 ints
        int vals[] = new int[5];
        // uninitialized - all zeros
        System.out.println("Initial vals array");
        showArray(vals);
        // give the array some values
        for (cnt = 0; cnt < vals.length; cnt++) {
            // assign a value
            vals[cnt] = (cnt + 1) * (cnt + 1);
        }
        System.out.println("vals array with some changes");
        showArray(vals);
        // declare an array and create with initializer list
        int second[] = { 2, 4, 6, 8};
        System.out.println("second array");
        showArray(second);
        
        // get set to actually create the array known as empty
        int size = 6;     // could be set by asking user, finding needed size in a file, or calculations
        empty = new int[size]; // the elements are set to zero, since primitive type
        empty[0] = 3;   // valid - array doesn't exist - compiler catches
        System.out.println("revised, not so empty array");
        showArray(empty);
        
        // try to go outside the bounds - crash ArrayIndexOutOfBounds exception
        //vals[5] = 42;
        // try to expand the array - doesn't do what was probably expected 
        //    - because entirely new array was created (initialized to zero) 
        //    - previous existing elements were blown away
        //vals = new int[size+1];
        //vals[5] = 37;
        //System.out.println("revised, expanded vals array");
        //showArray(vals);
        
        // instead must create a new array, copy contents
        int expanded [] = new int[size+1];
        expanded[5] = 37;
        // copy previous contents
        System.arraycopy(vals,0,expanded,0,vals.length);
        System.out.println("expanded array");
        showArray(expanded);
        
        // make a change - as would be expected, this changes the expanded array
        // but not the vals array it was copied from - but see TestBankExHand
        // to see differnet behaviour when working with array of objects
        expanded[3] = 13;
        System.out.println("vals[3]: " + vals[3]);
        System.out.println("expanded[3]: " + expanded[3]);
        
        // now, getting back to the original aim - expanding an existing array
        // presumably you want this back in the same variable so code can go on
        vals = expanded; // now points to the SAME array
        // display the arrays
        System.out.println("expanded vals array (gee it is the same): ");
        showArray(vals);
        System.out.println("expanded array: ");
        showArray(expanded);
        // make a change - perhaps surprisingly to many, this changes the expanded array
        // AND the vals array - since both variables really are referencing 
        // the same array 
        expanded[6] = 49;
        System.out.println("vals[6]: " + vals[6]);
        System.out.println("expanded[6]: " + expanded[6]);
        
        
        // make a copy - but make it a clone
        // clone returns an Object - which an array is 
        // but to obtain an array, must use cast
        // clone can be used when the target array is going to be created now
        // while arraycopy needs the target array to already exist
        int myClone[] = (int[]) vals.clone();  
        System.out.println("clone of expanded vals array: ");
        showArray(myClone);
        
        // make a change - as would be expected, this changes the clone array
        // but not the vals array it was copied from - but see TestBankExHand
        // to see different behaviour when working with array of objects
        myClone[6] = 59;
        System.out.println("vals[6]: " + vals[6]);
        System.out.println("myClone[6]: " + myClone[6]);
        
        // array of arrays - sort of like multidimensional arrays - but don't have to be square
        //int table[][] = new int[][] { {0}, {0, 1}, {0, 1, 2}, {0, 1, 2, 3} };
        int table[][] =  { {0}, {0, 1}, {0, 1, 2}, {0, 1, 2, 3} };
        for (cnt = 0; cnt < table.length; cnt++){
            System.out.println("===");
            showArray(table[cnt]);
        }
    }
    
}