Task 1:
Calculating the area of a circle with a given radius.
package assignment1_donike;
public class CirlceArea {
public static void main(String[] args) {
// Defining double with Radius of circle
double rad = 4.00;
// Defining double that holds area, assigning Pi*(radius**2) using Math Method
double area = Math.PI * (rad * rad);
//Print area within sentence and one line
System.out.println("The radius of a circle with the radius "+rad+" is: "+area);
}
} Task 2
Calculating the area of a circle with a user give radius, catching errors caused by wrong input.
package assignment1_donike;
import java.io.BufferedReader; //using BR as instructed
import java.io.IOException; // No idea why i need to include that in line 18, but apparently I do
import java.io.InputStreamReader; //
public class CircleAreaUserInput {
// creating new method that calculates area of circle from radius
static double area_calc(double rad) {
// Defining double that holds area, assigning Pi*(radius**2) using Math Method
double area = Math.PI * (rad * rad);
//Print area within sentence and one line
return area;
} // method
public static void main(String[] args) throws IOException{
// Creating boolean as condition for while loop
boolean valid_input = false;
// Creating user input var bc. it will be filled later within try/catch block and needs to be in the global scope
double user_radius = 0;
// Start loop, continue while valid input boolean == false
while(valid_input == false) {
// Creating Buffer
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
// print prompt to user in console
System.out.print("Enter the Radius: ");
// read input line from console
String user_input = reader.readLine();
// Try conversion to double, if successful set user_radius as converted double & valid_input=true and thus exit loop
try {
user_radius = Double.valueOf(user_input);
System.out.println("Your input after Conversion is: " + user_radius);
valid_input = true;}
// If conversion to double fails, give error message in console and keep in loop because valid_input is still false
catch(Exception e) {
System.out.println("Your input is not valid, please enter an integer, double or float\n\n");}
}// close while loop
// Pass user radius to method
System.out.println("The area of a circle with the radius " + user_radius + " is " + area_calc(user_radius));
} // close public static void main
} // close class
Task 3
Calculating the first 20 Fibonacci sequence numbers.
package assignment1_donike;
public class Fibonacci {
public static void main(String[] args) {
// starting points for additions are 0 and 1
int a = 0;
int b = 1;
// current will hold the value of the current addition of the two previous values and thus the Fibonacci number
int current = 0;
// counter will count iterations
int counter = 1;
while (counter<=20) {
// Addition of two previous numbers to get current Fib. value
current = a+b;
// Print counter of Fib. numbers and value at this position
System.out.println("Fibonacci Nr.\t"+counter+"\tis\t"+current+"\n");
// Change values to new positions: starting point (a) becomes what previously was 2nd summand
a = b;
// current Fib. value will become the 2nd summand in next iteration
b = current;
// increment counter + 1 to keep track of iterations
counter = counter+1;
} // close while loop
} //close public static void
} // close class
