update,

it114105/itp3914/Lab04/Ex1.java

@@ -0,0 +1,13 @@
+import java.util.Scanner;
+
+public class Ex1 {
+    public static void main(String[] args) {
+        Scanner input = new Scanner(System.in);
+        double r, l;
+        System.out.print("Enter radius: ");
+        r = input.nextDouble();
+        System.out.print("Enter length: ");
+        l = input.nextDouble();
+        System.out.printf("volume = %.2f\n", (r*r*Math.PI*l) );
+    }
+}

it114105/itp3914/Lab04/Ex3.java

@@ -0,0 +1,16 @@
+import java.util.Scanner;
+
+public class Ex3 {
+    public static void main(String[] args) {
+        Scanner input = new Scanner(System.in);
+        double a, b, c;
+        System.out.print("Please enter a: ");
+        a = input.nextDouble();
+        System.out.print("Please enter b: ");
+        b = input.nextDouble();
+        System.out.print("Please enter c: ");
+        c = input.nextDouble();
+        System.out.printf("x1 = %.2f, x2 = %.2f\n", ((-b+Math.sqrt(b*b - 4*a*c))/(2*a)), ((-b-Math.sqrt(b*b-4*a*c))/(2*a)));
+
+    }
+}

it114105/itp3914/Lab04/README.md.original

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+# Lab 4 Simple I/O
+## Topic 2.1-2.3: Variables, Data Types, Operators
+
+### Intended Learning Outcomes
+Upon completion of this tutorial/lab, you should be able to:
+- Use console screen to input/output data.
+- Use dialog box and message box to input/output data.
+
+#### Exercise 1 – Programming Exercise
+PROBLEM: Calculate the volume of a cylinder (with console I/O)
+
+Write a Java program that computes the volume ($v$) of a cylinder. The program should use Scanner class to read the radius ($r$) and the length ($l$), and compute the volume ($v$) with the formula:$ v = r^2\pi l$.
+
+#### Exercise 2 – Programming Exercise
+PROBLEM: Calculate the volume of a cylinder (with dialog and message boxes)
+
+Rewrite the program in Exercise 1 using dialog and message boxes in the `JOptionPane` class as the input/output method.
+
+#### Exercise 3 – Programming Exercise
+PROBLEM: Find the root(s) of a quadratic equation
+
+Write a Java program to calculate the two roots of a quadratic equation (ax2 + bx + c = 0) by using the formulae:
+
+```math
+x1 = \frac{-b+\sqrt{b^2-4ac}}{2a}, x2=\frac{-b-\sqrt{b^2-4ac}}{2a}
+```
+
+You can use `Math.sqrt(x)` method to calcuate $\sqrt{x}$ For example, the statement
+
+```java
+System.out.println(Math.sqrt(10));
+```
+prints the square root of 10. You are free to use either console I/O or `JOptionPane` classes.