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313 changes: 313 additions & 0 deletions src/main/java/com/thealgorithms/maths/MathToolkit.java
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/*
* MathToolkit.java
* A simple single-file Java project that provides a command-line math toolkit.
* All user-facing text is in English as requested.
*
* Features:
* - Basic arithmetic (addition, subtraction, multiplication, division)
* - GCD and LCM
* - Factorial (uses BigInteger for large results)
* - Fibonacci (n-th, uses BigInteger)
* - Prime check (BigInteger.isProbablePrime)
* - Quadratic equation solver (real and complex roots)
*
* Usage:
* Compile: javac MathToolkit.java
* Run: java MathToolkit
*
* Author: ChatGPT
*/

import java.math.BigInteger;
import java.util.InputMismatchException;
import java.util.Scanner;

public class MathToolkit {

private static final Scanner scanner = new Scanner(System.in);

public static void main(String[] args) {
System.out.println("Welcome to MathToolkit — a simple Java math project.");
boolean running = true;
while (running) {
printMenu();
System.out.print("Choose an option (1-9) or 0 to exit: ");
int choice = readInt();
System.out.println();
switch (choice) {
case 0:
running = false;
System.out.println("Goodbye!");
break;
case 1:
basicArithmetic();
break;
case 2:
gcdLcm();
break;
case 3:
factorial();
break;
case 4:
fibonacci();
break;
case 5:
primeCheck();
break;
case 6:
quadraticSolver();
break;
case 7:
integerOperationsDemo();
break;
case 8:
about();
break;
case 9:
help();
break;
default:
System.out.println("Invalid option — please try again.");
}
System.out.println();
}
scanner.close();
}

private static void printMenu() {
System.out.println("=== MathToolkit Menu ===");
System.out.println("1) Basic arithmetic ( +, -, *, / )");
System.out.println("2) GCD and LCM");
System.out.println("3) Factorial (BigInteger)");
System.out.println("4) Fibonacci (n-th term, BigInteger)");
System.out.println("5) Prime check");
System.out.println("6) Quadratic equation solver");
System.out.println("7) Integer operations demo (safe long handling)");
System.out.println("8) About this project");
System.out.println("9) Help (short usage)");
System.out.println("0) Exit");
}

private static void basicArithmetic() {
System.out.println("-- Basic arithmetic --");
System.out.print("Enter first number: ");
double a = readDouble();
System.out.print("Enter second number: ");
double b = readDouble();
System.out.println("Choose operator: + - * /");
System.out.print("Operator: ");
String op = scanner.next();
double result;
switch (op) {
case "+":
result = a + b;
System.out.printf("Result: %.10g\n", result);
break;
case "-":
result = a - b;
System.out.printf("Result: %.10g\n", result);
break;
case "*":
result = a * b;
System.out.printf("Result: %.10g\n", result);
break;
case "/":
if (b == 0) {
System.out.println("Error: Division by zero is not allowed.");
} else {
result = a / b;
System.out.printf("Result: %.10g\n", result);
}
break;
default:
System.out.println("Unknown operator.");
}
}

private static void gcdLcm() {
System.out.println("-- GCD and LCM --");
System.out.print("Enter first integer (long): ");
long a = readLong();
System.out.print("Enter second integer (long): ");
long b = readLong();
long g = gcd(a, b);
long l = lcm(a, b);
System.out.println("GCD(" + a + ", " + b + ") = " + g);
System.out.println("LCM(" + a + ", " + b + ") = " + l);
}

private static void factorial() {
System.out.println("-- Factorial --");
System.out.print("Enter a non-negative integer (n): ");
int n = readNonNegativeInt();
BigInteger fact = factorialBig(n);
System.out.println(n + "! = " + fact.toString());
}

private static void fibonacci() {
System.out.println("-- Fibonacci (n-th) --");
System.out.print("Enter n (0-based index, non-negative): ");
int n = readNonNegativeInt();
BigInteger fib = fibonacciBig(n);
System.out.println("Fibonacci(" + n + ") = " + fib.toString());
}

private static void primeCheck() {
System.out.println("-- Prime check --");
System.out.print("Enter integer to check (positive): ");
long n = readLongPositive();
BigInteger big = BigInteger.valueOf(n);
boolean probablePrime = big.isProbablePrime(12); // 12 -> sufficiently small error probability
if (probablePrime) {
System.out.println(n + " is probably prime.");
} else {
System.out.println(n + " is composite (not prime).");
}
}

private static void quadraticSolver() {
System.out.println("-- Quadratic equation solver: ax^2 + bx + c = 0 --");
System.out.print("Enter a (non-zero): ");
double a = readDoubleNonZero();
System.out.print("Enter b: ");
double b = readDouble();
System.out.print("Enter c: ");
double c = readDouble();
double disc = b * b - 4 * a * c;
if (disc > 0) {
double r1 = (-b + Math.sqrt(disc)) / (2 * a);
double r2 = (-b - Math.sqrt(disc)) / (2 * a);
System.out.printf("Two real roots: x1 = %.10g, x2 = %.10g\n", r1, r2);
} else if (disc == 0) {
double r = -b / (2 * a);
System.out.printf("One real root: x = %.10g\n", r);
} else {
double real = -b / (2 * a);
double imag = Math.sqrt(-disc) / (2 * a);
System.out.printf("Two complex roots: x1 = %.10g + %.10gi, x2 = %.10g - %.10gi\n", real, imag, real, imag);
}
}

private static void integerOperationsDemo() {
System.out.println("-- Integer operations demo --");
System.out.println("This demonstrates safe handling with long and BigInteger when needed.");
System.out.print("Enter a long integer: ");
long a = readLong();
System.out.print("Enter another long integer: ");
long b = readLong();
System.out.println("Sum as long: " + (a + b));
BigInteger bigSum = BigInteger.valueOf(a).add(BigInteger.valueOf(b));
System.out.println("Sum as BigInteger: " + bigSum.toString());
}

private static void about() {
System.out.println("MathToolkit — single-file Java project. All text is English.");
System.out.println("Feel free to request additional features or a multi-file project structure.");
}

private static void help() {
System.out.println("Help: Use options from the menu, input numbers when asked.");
System.out.println("For large factorial or Fibonacci values, the program uses BigInteger.");
}

// --- Utility math functions ---

private static long gcd(long a, long b) {
a = Math.abs(a);
b = Math.abs(b);
if (a == 0) return b;
if (b == 0) return a;
while (b != 0) {
long t = a % b;
a = b;
b = t;
}
return Math.abs(a);
}

private static long lcm(long a, long b) {
a = Math.abs(a);
b = Math.abs(b);
if (a == 0 || b == 0) return 0;
return Math.abs(a / gcd(a, b) * b);
}

private static BigInteger factorialBig(int n) {
BigInteger result = BigInteger.ONE;
for (int i = 2; i <= n; i++) {
result = result.multiply(BigInteger.valueOf(i));
}
return result;
}

private static BigInteger fibonacciBig(int n) {
if (n == 0) return BigInteger.ZERO;
if (n == 1) return BigInteger.ONE;
BigInteger prev = BigInteger.ZERO, curr = BigInteger.ONE;
for (int i = 2; i <= n; i++) {
BigInteger next = prev.add(curr);
prev = curr;
curr = next;
}
return curr;
}

// --- Robust input helpers ---

private static int readInt() {
while (true) {
try {
return scanner.nextInt();
} catch (InputMismatchException ex) {
System.out.print("Invalid integer — please enter again: ");
scanner.next();
}
}
}

private static int readNonNegativeInt() {
while (true) {
int v = readInt();
if (v < 0) System.out.print("Please enter a non-negative integer: ");
else return v;
}
}

private static long readLong() {
while (true) {
try {
return scanner.nextLong();
} catch (InputMismatchException ex) {
System.out.print("Invalid long — please enter again: ");
scanner.next();
}
}
}

private static long readLongPositive() {
while (true) {
long v = readLong();
if (v <= 0) System.out.print("Please enter a positive integer: ");
else return v;
}
}

private static double readDouble() {
while (true) {
try {
return scanner.nextDouble();
} catch (InputMismatchException ex) {
System.out.print("Invalid number — please enter again: ");
scanner.next();
}
}
}

private static double readDoubleNonZero() {
while (true) {
double v = readDouble();
if (v == 0.0) System.out.print("Value cannot be zero — please enter again: ");
else return v;
}
}
}
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