Refactoring Techniques in Java

Introduction

Hello, Explorer! Today is about refactoring . Consider it as organizing your favorite toys in the toybox. We're going to learn about the Extract Method, Rename Method, and Substitute Algorithm refactorings. Refactoring helps us make our code cleaner and neater while keeping the functionality the same!

Refactoring Overview

Imagine having a complex map. Refactoring transforms it into simpler directions. Our code gets rearranged to make it more readable and efficient without altering what it does. Let's consider a small code snippet before and after refactoring: Java // Before refactoring public double calculate(double total, int quantity) {double price = total / quantity; double tax = price * 0.2; double totalPrice = price + tax; return totalPrice;} // After refactoring public double calculateTotalPrice(double total, int quantity) {double price = calculatePrice(total, quantity); double tax = calculateTax(price); return price + tax;} public double calculatePrice(double total, int quantity) {return total / quantity;} public double calculateTax(double price) {return price * 0.2;} Both versions of the code do the same thing, but the latter is simpler and easier to understand!

Understanding the Extract Method

Imagine a large recipe for a complete breakfast. The Extract Method technique is like having separate recipes for eggs, toast, coffee, etc., instead of one large recipe. Take a look at this code: Java // Before refactoring public String greetUser(String username) {username = username.trim().toLowerCase(); // Prepare the username String message = "Hello, " + username + "!"; // Prepare the message return message; // Return the prepared message} // After refactoring public String cleanUsername(String username) {return username.trim().toLowerCase(); // Returns a cleaned version of the username} public String greetUser(String username) {username = cleanUsername(username); // Clean the username String message = "Hello, " + username + "!"; // Prepare and return the message return message;} // Before refactoring public String greetUser(String username) {username = username.trim().toLowerCase(); // Prepare the username String message = "Hello, " + username + "!"; // Prepare the message return message; // Return the prepared message} // After refactoring public String cleanUsername(String username) {return username.trim().toLowerCase(); // Returns a cleaned version of the username} public String greetUser(String username) {username = cleanUsername(username); // Clean the username String message = "Hello, " + username + "!"; // Prepare and return the message return message;} Here, we moved the username preparation from greetUser into its own function cleanUsername . Nice and tidy!

Using Rename Method

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Java

// Before refactoring
public String greetUser(String username) {
    username = username.trim().toLowerCase(); // Prepare the username
    String message = "Hello, " + username + "!"; // Prepare the message
    return message; // Return the prepared message
}

// After refactoring
public String cleanUsername(String username) {
    return username.trim().toLowerCase(); // Returns a cleaned version of the username
}

public String greetUser(String username) {
    username = cleanUsername(username); // Clean the username
    String message = "Hello, " + username + "!"; // Prepare and return the message
    return message;
}

Java

// Before refactoring
public double fx(double x) {
    return 3.14 * (x * x); // Calculates a value that is pi times the square of x
}

// After refactoring
public double calculateCircleArea(double radius) {
    return 3.14 * (radius * radius); // Calculates the area of a circle with a given radius
}

// Before refactoring
public double fx(double x) {
    return 3.14 * (x * x); // Calculates a value that is pi times the square of x
}

// After refactoring
public double calculateCircleArea(double radius) {
    return 3.14 * (radius * radius); // Calculates the area of a circle with a given radius
}

Java

// Before refactoring
public int findSmallest(int[] numbers) {
    int smallest = Integer.MAX_VALUE;
    for (int num : numbers) {
        if (num < smallest) {
            smallest = num;
        }
    }
    return smallest;
}

// After refactoring
import java.util.Collections;
import java.util.Arrays;
import java.util.List;

public int findSmallest(int[] numbers) {
    List<Integer> numberList = Arrays.stream(numbers).boxed().toList();
    return Collections.min(numberList); // Returns the smallest number from 'numbers'
}

// Before refactoring
public int findSmallest(int[] numbers) {
    int smallest = Integer.MAX_VALUE;
    for (int num : numbers) {
        if (num < smallest) {
            smallest = num;
        }
    }
    return smallest;
}

// After refactoring
import java.util.Collections;
import java.util.Arrays;
import java.util.List;

public int findSmallest(int[] numbers) {
    List<Integer> numberList = Arrays.stream(numbers).boxed().toList();
    return Collections.min(numberList); // Returns the smallest number from 'numbers'
}

Java

// Before refactoring
public double fx(double x) {
    return 3.14 * (x * x); // Calculates a value that is pi times the square of x
}

// After refactoring
public double calculateCircleArea(double radius) {
    return 3.14 * (radius * radius); // Calculates the area of a circle with a given radius
}

Java

// Before refactoring
public int findSmallest(int[] numbers) {
    int smallest = Integer.MAX_VALUE;
    for (int num : numbers) {
        if (num < smallest) {
            smallest = num;
        }
    }
    return smallest;
}

// After refactoring
import java.util.Collections;
import java.util.Arrays;
import java.util.List;

public int findSmallest(int[] numbers) {
    List<Integer> numberList = Arrays.stream(numbers).boxed().toList();
    return Collections.min(numberList); // Returns the smallest number from 'numbers'
}

Introduction

Refactoring Overview

Understanding the Extract Method

Using Rename Method

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Discovering Substitute Algorithm

Lesson Summary