mcsee

public class Person {
    private List<String> hobbies;

    public Person(List<String> hobbies) {
        this.hobbies = new ArrayList<>(hobbies);
    }

    public List<String> hobbies() {
        // This returns a shallow copy
        // This is usually not a big performance issue

mcsee

public class Person {
    private List<String> hobbies;

    public Person(List<String> hobbies) {
        this.hobbies = hobbies;
    }

    public List<String> getHobbies() {
        return hobbies;
    }

mcsee

// Step 1: Find or Create a Polymorphic Hierarchy

abstract class MicrophoneState { }
final class On extends MicrophoneState { }
final class Off extends MicrophoneState { }

// Step 2: Move the Body of Each IF to the Corresponding Abstraction

abstract class MicrophoneState {
    public abstract String polymorphicMethodFromIf();

mcsee

public String handleMicrophoneState(String state) {
    if (state.equals("off")) {
        return "Microphone is off";
    } else {
        return "Microphone is on";
    }
}

/* The constant representing the 'off' state is
duplicated throughout the code, 

mcsee

public class TransactionService {
    private EntityManager entityManager;

    public TransactionService(EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    public void saveTransaction(Transaction transaction) {
        entityManager.getTransaction().begin();
        entityManager.persist(transaction);

mcsee

// Domain classes
abstract class Transaction {
    private String id;
    private double amount;
}

class BankTransaction extends Transaction {
    private String bankName;
}

mcsee

<?php

class AccessControlPanel {

  private $users = [];

  // 1.  Make a contextual copy of the repeated code
  
  private function createUser(
     $username, 

mcsee

<?php

class AccessControlPanel {

  private $users = [];

  public function createRegularUser($username, $password, $email) {
    $user = [
      "username" => $username,
      "email" => $email,

mcsee

public class BlackHole
{
  public double Mass { get; private set; }
  public double SchwarzschildRadius { get; private set; }
  public bool HasSingularity { get; } // Always true for a black hole

  public BlackHole(double mass)
  {
    Mass = mass;
    SchwarzschildRadius = CalculateSchwarzschildRadius(mass);

mcsee

// Define the gravitational constant
const G = 6.67430e-11; // m^3 kg^-1 s^-2

/**
 * Calculate the gravitational force between two masses.
 * @param {number} m1 - Mass of the first object in kilograms.
 * @param {number} m2 - Mass of the second object in kilograms.
 * @param {number} r - Distance between the centers of the masses in meters.
 * @returns {number} - Gravitational force in Newtons.
 */