Exceptions.java

import java.awt.Point;

public class Main {
	public static void printMatrix(int[][] mat) {
		for (int i = 0; i < mat.length; i++) 
		{
			for (int j = 0; j < mat.length; j++)
				System.out.print(mat[i][j] + " ");
			System.out.print("\n");
		}
	}
	
	public static void handleDefault() {
		Io.print("You have to choose between 1-3");
	}
	
	/*
	 * grades 
	 */
	public static void task1() {
		int[] grades = new int[6];
		int counter = 0, sum = 0;
		double avg;
		
		for (int i = 0; i < grades.length; i++) {
			grades[i] = Io.promptInt("enter grade for " + (i + 1) + ": ");
			try {
				if (grades[i] > 100)
					throw new Exception("illegal grade.");
				else if (grades[i] < 0)
					throw new Exception("grades cannot be negative.");
				else {
					counter++;
					sum += grades[i];
				}
			}
			
			catch (Exception e) {
				Io.print(e.getMessage());
			}
		}
		
		avg = (double)sum / counter;
		Io.print("avg: " + avg);
		Io.print("amount of legal grades: " + avg);
	}
	
	/*
	 * chess
	 */
	public static void task2() {
		int[][] matrix = new int[8][8];
		int row, col, prevRow = 5, prevCol = 7, counter = 0;
		char cont;
//		boolean ok = false;
		// placing the horse
		matrix[prevRow][prevCol] = 1;
		printMatrix(matrix);
		// getting new position from user
		do {	
			row = Io.promptInt("enter new row:");
			col = Io.promptInt("enter new column:");
			
			try {
				if (Math.abs(prevRow - row) == 2 && Math.abs(prevCol - col) == 1 || Math.abs(prevRow - row) ==  1 && Math.abs(prevCol - col) == 2) {
					matrix[row][col] = 1;
					matrix[prevRow][prevCol] = 0;
					prevRow = row;
					prevCol = col;
				} else {
					throw new Exception("illegal horse move.");
				}
					
			}
			
			catch (ArrayIndexOutOfBoundsException e1) {
				Io.print("HEY! The new points are not in the matrix, Neo.");
				counter++;
			}
			
			catch (Exception e2) {
				Io.print(e2.getMessage());
				counter++;
			}
			
			finally {
				Io.print("horse position: row: " + prevRow + ", col:" + prevCol);
				printMatrix(matrix);
			}
			
			// end
			Io.print("do you wish to continue? [y/n]");
			cont = Io.readChar();
		} while (cont != 'n');
		
		Io.print("amount of illegal movements: " + counter);
	}
	
	/*
	 * example 4
	 */
	public static void task3() {
		boolean negative, outOfBounds;
		int i, j, counter = 0, sum = 0;
		int[] a = new int[5];
		for (i = 0; i < 5; i++) {
			for (j = 0; j < 6; j++) {
				negative = false;
				outOfBounds = false;
				try {
					Io.print(i + ": " + a[i]);
					if (a[i] < 0)
						throw new Exception("-");
				}
				
				catch (ArrayIndexOutOfBoundsException e) {
					Io.print("error");
					counter++;
					outOfBounds = true;
				}
				
				catch (Exception e2) {
					if (e2.getMessage() == "-")
						negative = true;
				}
				
				finally {
					if (!negative && !outOfBounds)
						sum += a[i];
				}
			}
		}
	}
	
	/*
	 * none-null counter
	 */
	public static void task4() {
		int counter = 0;
		Point[] points = new Point[5];
		points[2] = new Point(4, 5);
		points[0] = new Point(0, 10);
		
		for (int i = 0; i < points.length; i++) {
			try {	
					if (points[i] == null) 
						throw new Exception("no pointer: " + i);
					
					else 
						Io.print("there is a pointer for " + i);
					
			}
			
			catch (Exception e) {
				Io.print(e.getMessage());
				counter++;
			}
		}
		
		Io.print("amount of none-null obejcts: " + (points.length - counter));
	}
	
	public static void main(String[] args) {
		int choice;
		
		do {
			choice = Io.promptInt("enter your choice (1-4):");
		} while (choice < 1 || choice > 4);
		
		switch(choice) {
			case 1: 
				task1();
				break;
				
			case 2: 
				task2();
				break;
				
			case 3: 
				task3();
				break;
				
			case 4:
				task4();
				break;
				
			default:
				handleDefault();
				break;
		}
	}
}