Simple CLI Calculator

A Java-based command-line calculator application with a clean, modular architecture.

Features

• Basic Arithmetic Operations: Addition, subtraction, multiplication, division
• Advanced Operations: Power (exponentiation), square root
• Multiple Input Formats:
  • Mathematical expressions: 5 + 3, 10 * 2
  • Command format: add 5 3, sqrt 25
• Error Handling: Division by zero, invalid input, negative square roots
• Interactive CLI: Help system, clear screen, graceful exit

Project Structure

src/
├── main/
│   └── Main.java              # Entry point and main program loop
├── calculator/
│   └── Calculator.java        # Core calculation logic
├── input/
│   └── InputHandler.java      # Input parsing and validation
├── operations/
│   └── Operation.java         # Enum defining supported operations
└── utils/
    ├── NumberParser.java      # Number parsing utilities
    └── StringUtils.java       # String manipulation utilities

How to Build and Run

Prerequisites

• Java 8 or higher
• Command line terminal

Compilation

# Navigate to the project directory
cd "/home/ashish/Documents/code/Java/First Project"

# Compile all Java files
javac -d bin src/**/*.java

# Alternative: Compile with classpath
javac -cp src -d bin src/main/Main.java src/calculator/Calculator.java src/input/InputHandler.java src/operations/Operation.java src/utils/NumberParser.java src/utils/StringUtils.java

Running

# Run the application
java -cp bin main.Main

Usage Examples

Mathematical Expressions

> 5 + 3
Result: 8

> 10.5 * 2
Result: 21

> 15 / 3
Result: 5

> 2 ^ 8
Result: 256

Command Format

> add 5 3
Result: 8

> mul 4.5 2
Result: 9

> sqrt 16
Result: 4

> pow 2 10
Result: 1024

Special Commands

> help          # Show help information
> clear         # Clear the screen
> exit          # Exit the calculator

Supported Operations

Operation	Symbols	Command	Example
Addition	+	add	5 + 3 or add 5 3
Subtraction	-	sub, subtract	5 - 3 or sub 5 3
Multiplication	*	mul, multiply	5 * 3 or mul 5 3
Division	/	div, divide	15 / 3 or div 15 3
Power	^	pow, power	2 ^ 3 or pow 2 3
Square Root	sqrt	sqrt, squareroot	sqrt 25

Error Handling

The calculator handles various error conditions:

• Division by zero: Returns appropriate error message
• Negative square root: Not supported for real numbers
• Invalid input: Clear error messages with suggestions
• Missing operands: Validates correct number of arguments

Architecture Highlights

• Modular Design: Each class has a single responsibility
• Extensible: Easy to add new operations via the Operation enum
• Robust Input Handling: Supports multiple input formats
• Clean Separation: Business logic separated from UI concerns
• Utility Classes: Reusable components for common operations

Future Enhancements

Potential features that could be added:

• Memory operations (store/recall)
• History of calculations
• More advanced mathematical functions (trigonometry, logarithms)
• Expression parsing with parentheses support
• Configuration file for custom settings