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
-
- total, num
- for loop
- public, class, int, for
- It adds the value of num to the variable total
- total = 0
- 10 numbers
- It asks the user to enter ten integer numbers, finds their total and displays it on screen.
- 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
- A class defines a new data type which once defined can be used to create objects of that type.
- public class Ellipse {
double radius1, radius2;double Calc_Area( ) {
return (Math.PI * radius1 * radius2);
}
} - 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
- A class defines a new data type which once defined can be used to create objects of that type.
- 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));
}
} - public class Shapes {
public static void main (String args[]) {
Square s = new Square();
s.length = 5;
s.displayArea();
s.displayPerimeter();
}
}