Swing-Calculator-U23ST1021

JOY BAWA MUSA U23ST1021 CSC 201 ASSIGNMENT

1. Overview

The Java Swing Calculator is a simple GUI-based calculator application designed using Java's

Swing framework. It allows users to perform basic arithmetic operations such as addition,

subtraction, multiplication, division, exponentiation, and square root calculation. The

application uses the JavaScript engine (via ScriptEngineManager) to evaluate mathematical

expressions dynamically.

2. What is Needed to Build the Program

Prerequisites:

To build and run the Java Swing Calculator, you need the following:

• Java Development Kit (JDK) 11 or later: To compile and run the Java program.

• Integrated Development Environment (IDE): (Optional) IntelliJ IDEA, Eclipse, or

NetBeans for a better development experience.

• Text Editor: (Optional) Notepad++, VS Code, or any preferred editor.

• Command Line/Terminal: To compile and execute the program if not using an IDE.

Required Libraries:

• Java Swing (𝑗𝑎𝑣𝑎𝑥.𝑠𝑤𝑖𝑛𝑔.∗): For building the graphical user interface.

• AWT (𝑗𝑎𝑣𝑎.𝑎𝑤𝑡.∗): For layout and event handling.

• Java Scripting (𝑗𝑎𝑣𝑎𝑥.𝑠𝑐𝑟𝑖𝑝𝑡.∗): For evaluating mathematical expressions

dynamically.

3. Features:

• Graphical User Interface (GUI) using Java Swing

• Basic arithmetic operations: +,−,∗,/

• Exponentiation (^)

• Square root calculation (√)

• Parentheses for grouping expressions

• Error handling for invalid input, division by zero, and unbalanced parentheses

• Clear (𝐶) button to reset input

4. How It Works:

User Interface;

• A JTextField is used as a display to show the input and results.

• A JPanel with a GridLayout(5,4,5,5) arranges the calculator buttons.

• Buttons include digits (0-9), operators (+,−,∗,/,^), special functions (√, 𝐶, =), and

parentheses ((, )).

Event Handling;

• Implements ActionListener to handle button clicks.

• When a button is clicked, its corresponding value is appended to the input string (StringBuilder).

• The display updates dynamically to show the input.

• Pressing = triggers expression evaluation.

• Pressing 𝐶 clears the input.

• Pressing √ calculates the square root of the current input.

Expression Evaluation;

• The program utilizes the ScriptEngine from Java's ScriptEngineManager to evaluate mathematical expressions.

• The ^ operator (exponentiation) is replaced with ** for compatibility with the

JavaScript engine;

• Parentheses balance is checked before evaluation.

• Errors such as division by zero, invalid expressions, and negative square roots are handled appropriately.

5. Implementation Details:

Class Structure;

p𝑢𝑏𝑙𝑖𝑐 𝑐𝑙𝑎𝑠𝑠 𝑆𝑤𝑖𝑛𝑔𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑜𝑟 𝑒𝑥𝑡𝑒𝑛𝑑𝑠 𝐽𝐹𝑟𝑎𝑚𝑒 𝑖𝑚𝑝𝑙𝑒𝑚𝑒𝑛𝑡𝑠 𝐴𝑐𝑡𝑖𝑜𝑛𝐿𝑖𝑠𝑡𝑒𝑛𝑒𝑟

• Extends 𝐽𝐹𝑟𝑎𝑚𝑒 to create a Swing-based window.

• Implements 𝐴𝑐𝑡𝑖𝑜𝑛𝐿𝑖𝑠𝑡𝑒𝑛𝑒𝑟 for handling button clicks.

Components;

• Display (𝐽𝑇𝑒𝑥𝑡𝐹𝑖𝑒𝑙𝑑): Shows user input and results.

• Buttons (𝐽𝐵𝑢𝑡𝑡𝑜𝑛): Contains numbers, operators, and function keys.

• Panel (𝐽𝑃𝑎𝑛𝑒𝑙): Organizes buttons in a grid layout.

Key Methods;

�𝑐𝑡𝑖𝑜𝑛𝑃𝑒𝑟𝑓𝑜𝑟𝑚𝑒𝑑(𝐴𝑐𝑡𝑖𝑜𝑛𝐸𝑣𝑒𝑛𝑡 𝑒)

Handles button clicks by updating input, performing calculations, or handling errors.

E𝑣𝑎𝑙𝑢𝑎𝑡𝑒𝐸𝑥𝑝𝑟𝑒𝑠𝑠𝑖𝑜𝑛()

• Replaces ^ with ∗∗ for JavaScript compatibility.

• Checks for balanced parentheses.

• Uses ScriptEngine to evaluate the expression.

• Handles division by zero and invalid input errors.

ℎ𝑎𝑛𝑑𝑙𝑒𝑆𝑞𝑢𝑎𝑟𝑒𝑅𝑜𝑜𝑡()

• Parses the current input as a number.

• Computes the square root if the number is non-negative.

• Displays an error message if the number is negative.

j𝑠𝑉𝑎𝑙𝑖𝑑𝐼𝑛𝑝𝑢𝑡(𝑆𝑡𝑟𝑖𝑛𝑔 𝑐𝑚𝑑)

• Ensures operators are not added consecutively.

• Allows numbers, parentheses, and valid operators.

j𝑠𝐵𝑎𝑙𝑎𝑛𝑐𝑒𝑑(𝑆𝑡𝑟𝑖𝑛𝑔 𝑒𝑥𝑝𝑟𝑒𝑠𝑠𝑖𝑜𝑛)

• Checks if parentheses in the expression are balanced.

6. Error Handling

• Invalid Expressions: Displays "Error: Invalid expression".

• Division by Zero: Displays "Error: Division by zero".

• Unbalanced Parentheses: Displays "Error: Unbalanced parentheses".

• Negative Square Root: Displays "Error: Negative √".

7. Execution

To run the program, compile and execute the Java file:

j𝑎𝑣𝑎𝑐 𝑆𝑤𝑖𝑛𝑔𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑜𝑟.𝑗𝑎𝑣𝑎

j𝑎𝑣𝑎 𝑆𝑤𝑖𝑛𝑔𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑜𝑟

Alternatively, execute it within an IDE like IntelliJ IDEA or Eclipse.

This Java Swing Calculator demonstrates effective GUI design and event handling in Java. The use of ScriptEngine enables flexible mathematical expression evaluation, while error handling ensures robustness. It serves as a functional and extensible calculator application.

NOTE: You must use a bracket while using the calculator for operations. Remember to close the bracket to avoid errors.