Common Java Refactorings: Techniques and Examples

Here are some common refactorings that can improve the design of a Java codebase:

Extract Method: This refactoring is used to move a section of code into a separate method. This can improve readability and make it easier to understand the code.

Example:

Before:

void printOrder(Order order) {
    System.out.println("Order:");
    System.out.println("Customer: " + order.getCustomer().getName());
    System.out.println("Order number: " + order.getNumber());
    System.out.println("Order total: " + order.getTotal());
}



After:

void printOrder(Order order) {
    printOrderDetails(order);
}

void printOrderDetails(Order order) {
    System.out.println("Order:");
    System.out.println("Customer: " + order.getCustomer().getName());
    System.out.println("Order number: " + order.getNumber());
    System.out.println("Order total: " + order.getTotal());
}

Extract Class: This refactoring is used to move a group of related fields and methods into a new class. This can improve encapsulation and make it easier to understand the code.

Example:

Before:

class Order {
    private String number;
    private Customer customer;
    private List<OrderLine> lines;

    public String getNumber() {
        return number;
    }

    public Customer getCustomer() {
        return customer;
    }

    public List<OrderLine> getLines() {
        return lines;
    }
}



After:

class Order {
    private OrderDetails details;
    private List<OrderLine> lines;

    public OrderDetails getDetails() {
        return details;
    }

    public List<OrderLine> getLines() {
        return lines;
    }
}

class OrderDetails {
    private String number;
    private Customer customer;

    public String getNumber() {
        return number;
    }

    public Customer getCustomer() {
        return customer;
    }
}

Rename Method: This refactoring is used to change the name of a method to make it more descriptive or consistent with the codebase. This can improve readability and make it easier to understand the code.

Example:

Before:

class Order {
    public void calc() {
        // code to calculate order total
    }
}

After:

class Order {
    public void calculateTotal() {
        // code to calculate order total
    }
}

These are just a few examples of common refactorings that can improve the design of a Java codebase. There are many more refactorings available, and the appropriate refactoring to use will depend on the specific code being refactored.

It’s important to note that refactoring should be done incrementally and with caution, as it can introduce bugs if not done correctly. It’s a good practice to have a good test coverage and run the tests after each refactoring step.

Java