Merge classes for Java Code refactoring
In Java, merging classes is a refactoring technique that merges associated classes into a larger class, typically used to eliminate situations of over refinement or duplicate work. The following is an example code to illustrate when merging class refactoring is necessary and the refactored code:
//Code before merging
class User {
private String firstName;
private String lastName;
public User(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
}
class Order {
private String orderNumber;
private double amount;
private User user;
public Order(String orderNumber, double amount, User user) {
this.orderNumber = orderNumber;
this.amount = amount;
this.user = user;
}
public String getOrderNumber() {
return orderNumber;
}
public double getAmount() {
return amount;
}
public User getUser() {
return user;
}
}
public class Main {
public static void main(String[] args) {
User user = new User("John", "Doe");
Order order = new Order("12345", 100.00, user);
System.out.println("Order " + order.getOrderNumber() + " belongs to " + order.getUser().getFirstName() + " " + order.getUser().getLastName());
}
}
In the above code, the 'User' and 'Order' classes have a close correlation, and the 'Order' class relies on the 'User' class to provide information related to the user. However, this correlation may lead to duplicate code and logical dispersion.
By merging these two classes, we can add the 'getFirstName()' and 'getLastName()' methods to the 'Order' class and directly access user information without passing through the 'User' object. The following is the code after merging and refactoring the class:
//Merged Code
class Order {
private String orderNumber;
private double amount;
private String firstName;
private String lastName;
public Order(String orderNumber, double amount, String firstName, String lastName) {
this.orderNumber = orderNumber;
this.amount = amount;
this.firstName = firstName;
this.lastName = lastName;
}
public String getOrderNumber() {
return orderNumber;
}
public double getAmount() {
return amount;
}
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
}
public class Main {
public static void main(String[] args) {
Order order = new Order("12345", 100.00, "John", "Doe");
System.out.println("Order " + order.getOrderNumber() + " belongs to " + order.getFirstName() + " " + order.getLastName());
}
}
In the refactored code, the 'Order' class contains all user related information, which can improve the readability and maintainability of the code and eliminate dependencies on the 'User' class.
The situation where classes need to be merged usually involves having a close association between two classes, but this association does not need to remain independent, or one class needs to use members of another class and does not want to be accessed through objects, thereby increasing the complexity of the code.
It should be noted that merging classes is not an unconditionally applicable refactoring technique and must be evaluated based on specific circumstances. In some scenarios, maintaining class independence and low coupling may be more important, while merging classes may cause code to become cluttered or difficult to maintain. Therefore, before conducting any refactoring, the advantages and disadvantages of various options should be carefully evaluated and weighed.
