PasswordGenerator.java

import java.util.Random;

public class PasswordGenerator {
    public final String UPPER = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    public final String LOWER = "abcdefghijklmnopqrstuvwxyz";
    public final String DIGIT = "0123456789";
    public final String SYMBOL = "@#$%&*=";

    public String generatePassword(int length, boolean useUpper, boolean useLower, boolean useDigits, boolean useSymbol) {
        StringBuilder allowedChars = new StringBuilder();
        if (useUpper) {
            allowedChars.append(UPPER);
        }
        if (useLower) {
            allowedChars.append(LOWER);
        }
        if (useDigits) {
            allowedChars.append(DIGIT);
        }
        if (useSymbol) {
            allowedChars.append(SYMBOL);
        }
        if(allowedChars.length() == 0) {
            throw new IllegalArgumentException("Error: At least one character type must be selected");
        }

        Random random = new Random();
        StringBuilder password = new StringBuilder();
        String allowed = allowedChars.toString();

        for (int i = 0; i < length; i++) {
            int index = random.nextInt(allowed.length());  // Randomly choose an index and get the character at that index from allowed characters
            password.append(allowed.charAt(index));
        }
        return password.toString();   // Change StringBuilder to String and return
    }
}