Resources for an introduction to JAVA programming textbook

Resources for the textbook An Introduction to JAVA Programming

Keyboard class

import java.io.*;
 public class Keyboard {
     public static String readString() {
         BufferedReader br;
         try {
             br = new BufferedReader(new InputStreamReader(System.in));
             return br.readLine();
         } catch (Exception e) {}
         return null;
     }
     public static int readInt() {
         return Integer.parseInt(readString());
     }
     public static byte readByte() {
         return Byte.parseByte(readString());
     }
     public static short readShort() {
         return Short.parseShort(readString());
     }
     public static long readLong() {
         return Long.parseLong(readString());
     }
     public static float readFloat() {
         return Float.parseFloat(readString());
     }
     public static double readDouble() {
         return Double.parseDouble(readString());
     }
     public static char readChar() {
         return readString().charAt(0);
     }
     public static boolean readBoolean() {
         return Boolean.parseBoolean(readString());
     }
 }

EasyScanner class

import java.util.*;
public class EasyScanner {
    public static int readInt() {
        Scanner sc = new Scanner(System.in);
        int i = sc.nextInt();
        return i;
    }
    public static double readDouble() {
        Scanner sc = new Scanner(System.in);
        double d = sc.nextDouble();
        return d;
    }
    public static String readString() {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        return s;
    }
    public static char readChar() {
        Scanner sc = new Scanner(System.in);
        char c = sc.next().charAt(0);
        return c;
    }
}
EasyScanner.java

Appendix 2 – Solutions

2.1   Paper 1 – Type question

1. • total, num
   • for loop
   • public, class, int, for
2. It adds the value of num to the variable total
3. total = 0
4. 10 numbers
5. It asks the user to enter ten integer numbers, finds their total and displays it on screen.
6. public class Total {
   public static void main (String args[]) {
   int total=0, num, i=0;
   while(i < 10) {
   System.out.println(“Enter a number:”);
   num = Keyboard.readInt();
   total+ = num;
   i++;
   }
   System.out.println(“Answer is ” + total);
   }
   }

2.2   Paper 2A – Type question

1. A class defines a new data type which once defined can be used to create objects of that type.
2. public class Ellipse {
   double radius1, radius2;double Calc_Area( ) {
   return (Math.PI * radius1 * radius2);
   }
   }
3. public class Shapes {
   public static void main (String args[]) {Ellipse e1 = new Ellipse();
   Ellipse e2 = new Ellipse();e1.radius1 = 1 + Math.random() * 10;
   e1.radius2 = 1 + Math.random() * 10;
   e2.radius1 = 1 + Math.random() * 10;
   e2.radius2 = 1 + Math.random() * 10;System.out.println(“Ellipse 1 has radii :”+ e1.radius1 +” and ” + e1.radius2);
   System.out.println(“Ellipse 2 has radii :”+ e2.radius1 +” and ” + e2.radius2);System.out.println(“The area of Ellipse 1 is : ” + e1.Calc_Area());
   System.out.println(“The area of Ellipse 2 is : ” + e2.Calc_Area());
   }
   }

2.3   Paper 2B – Type question

1. A class defines a new data type which once defined can be used to create objects of that type.
2. public class Square {
   int length;
   void displayArea() {
   System.out.println(“Area of Square : ” + (length*length));
   }
   void displayPerimeter() {
   System.out.println(“Perimiter of Square : ” + (4 * length));
   }
   }
3. public class Shapes {
   public static void main (String args[]) {
   Square s = new Square();
   s.length = 5;
   s.displayArea();
   s.displayPerimeter();
   }
   }