1. Overview
Passing many arguments to a method in Java can be challenging, especially when the number of arguments is large, or the data types are complex. In such cases, it can be challenging to understand the method’s purpose and maintain the code.
This article discusses some best practices for passing many arguments to Java methods.
2. Problem Statement
Suppose we have a method with many arguments:
public class VehicleProcessor {
Vehicle processVehicle(String make, String model, String color, int weight, boolean status) {
return new Vehicle(make, model, color, weight, status);
}
}
Passing many arguments to a method can be problematic for the code’s quality:
- By making the method signature harder to read and understand. It can be challenging to keep track of the order and purpose of each parameter, especially if the parameters have similar data types or are not well-named.
- By making adding or removing parameters difficult without affecting the calling code. Changing the signature of a method with many parameters can be time-consuming and error-prone, leading to increased maintenance costs and a higher risk of introducing bugs.
- By increasing the coupling between the caller and the method. If the caller is tightly coupled to the method signature, any changes to the signature can cause issues with the calling code.
- By increasing the risk of errors, such as passing the wrong parameter type or parameters in the wrong order. This can lead to bugs that can be difficult to track down.
- By increasing the difficulty of handling optional or default values. This can lead to code duplication or the creation of multiple methods with slightly different parameter lists, reducing the flexibility of the code.
- By impacting efficiency, especially if the arguments are large or complex data types. Passing a single object encapsulating all the required data can be more efficient.
Design patterns such as the Parameter Object Pattern, Java Bean Pattern, Java Varargs, or Builder Pattern can mitigate these issues and make our code more readable, maintainable, and efficient.
3. Java Object
The Parameter Object Pattern and the Java Bean Pattern are design patterns we use in Java to pass data between objects. Although they have some similarities, they also have some significant differences.
One of the key differences between these patterns is that Parameter Objects are often designed as immutable classes, while Java Bean classes are mutable. Another difference between the two patterns is their methods of instantiation.
Parameter Objects are helpful when there are many required parameters, and immutability is important. At the same time, we use Java Beans when we need to modify the object’s state at different times during its lifetime.
Let’s see an example of calling a method by passing multiple arguments before we go into in-depth discussions of each pattern:
VehicleProcessor vehicleProcessor = new VehicleProcessor();
vehicleProcessor.processVehicle("Ford", "Focus", "red", 2200, true);
3.1. Parameter Object
The Parameter Object Pattern is a pattern where we pass to a method a single object containing all the required parameters. At the same time, this practice can make the method signature more readable and maintainable.
Now, let’s create a class that holds all the required fields instead of having a method with many parameters:
public class Vehicle {
static String defaultValue = "DEFAULT";
private String make = defaultValue;
private String model = defaultValue;
private String color = defaultValue;
private int weight = 0;
private boolean statusNew = true;
public Vehicle() {
super();
}
public Vehicle(String make, String model, String color, int weight, boolean statusNew) {
this.make = make;
this.model = model;
this.color = color;
this.weight = weight;
this.statusNew = statusNew;
}
public Vehicle(Vehicle vehicle) {
this(vehicle.make, vehicle.model, vehicle.color, vehicle.weight, vehicle.statusNew);
}
}
Then, we can pass an instance of that class to the method:
Vehicle vehicle = new Vehicle("Ford", "Focus", "red", 2200, true);
vehicleProcessor.processVehicle(vehicle);
The advantages of this approach are:
3.2. Java Bean
The JavaBean pattern is similar to the parameter object approach. Still, it allows the object to be created with a no-argument constructor and then be modified or updated at different times during the object’s lifetime using setter methods.
Let’s create a JavaBean object having a no-argument constructor and getters and setters for every argument:
public class Motorcycle extends Vehicle implements Serializable {
private int year;
private String features = "";
public Motorcycle() {
super();
}
public Motorcycle(String make, String model, String color, int weight, boolean statusNew, int year) {
super(make, model, color, weight, statusNew);
this.year = year;
}
public Motorcycle(Vehicle vehicle, int year) {
super(vehicle);
this.year = year;
}
// standard setters and getters
}
Using the JavaBean pattern, we can access the fields using standard getters and setters, simplifying the code and updating objects during their lifetimes:
Motorcycle motorcycle = new Motorcycle("Ducati", "Monster", "yellow", 235, true, 2023);
motorcycle.setFeatures("GPS");
vehicleProcessor.processVehicle(motorcycle);
One of the main drawbacks of using Java Beans for passing arguments to a method is that we need a separate class that contains getter and setter methods for each argument, leading to verbosity and unnecessary complexity. Additionally, Java Beans are unsuitable for immutable objects, as they rely on the mutable state through their getter and setter methods.
4. Java Varargs
Another effective practice is using Java’s varargs feature, which allows a method to accept a variable number of arguments of a specified type:
public void addMotorcycleFeatures(String... features) {
StringBuilder str = new StringBuilder(this.getFeatures());
for (String feature : features) {
if (!str.isEmpty())
str.append(", ");
str.append(feature);
}
this.setFeatures(str.toString());
}
This practice is helpful if the number of arguments is not fixed and may vary depending on the situation.
Let’s use the varargs feature to call the method with any number of strings:
Motorcycle motorcycle = new Motorcycle("Ducati", "Monster", "red", 350, true, 2023);
motorcycle.addMotorcycleFeatures("abs");
motorcycle.addMotorcycleFeatures("navi", "charger");
motorcycle.addMotorcycleFeatures("wifi", "phone", "satellite");
Remember that using varargs with huge arguments can cause performance issues, so using them wisely is essential.
The limitations of Java Varargs include being applicable only for arguments of the same type, potentially reducing code readability when dealing with many arguments, and the inability to be used in combination with other variable arguments.
These drawbacks can limit the usefulness of Varargs in more complex scenarios and when dealing with diverse argument types.
5. Builder Pattern
Another widespread practice is the Builder pattern, which allows us to create an object step-by-step fluently and readably.
This pattern is also helpful for creating immutable objects.
For example, if we have a class with several fields and want to create immutable instances of this class, we could define a constructor with arguments for each field:
public class Car {
private final String make;
private final String model;
private final int year;
private final String color;
private final boolean automatic;
private final int numDoors;
private final String features;
public Car(String make, String model, int year, String color, boolean automatic, int numDoors, String features) {
this.make = make;
this.model = model;
this.year = year;
this.color = color;
this.automatic = automatic;
this.numDoors = numDoors;
this.features = features;
}
}
While this constructor is simple, it’s not extensible or flexible:
- If we want to add more fields to the Car class, we need to modify the constructor and the calling code, which can be cumbersome.
- If we want to create instances of Car with some optional fields or default values, we need to create overloaded constructors or use null values, making the code harder to read and maintain.
To address these issues, we can use the Builder Pattern to create immutable instances of the Car class.
First, we introduce a CarBuilder class that has methods for setting each field of the Car class:
public static class CarBuilder {
private final String make;
private final String model;
private final int year;
private String color = "unknown";
private boolean automatic = false;
private int numDoors = 4;
private String features = "";
public CarBuilder(String make, String model, int year) {
this.make = make;
this.model = model;
this.year = year;
}
public CarBuilder color(String color) {
this.color = color;
return this;
}
public CarBuilder automatic(boolean automatic) {
this.automatic = automatic;
return this;
}
public CarBuilder numDoors(int numDoors) {
this.numDoors = numDoors;
return this;
}
public CarBuilder features(String features) {
this.features = features;
return this;
}
public Car build() {
return new Car(this);
}
}
The Car class itself has a private constructor that takes a CarBuilder instance and uses it to create a new Car object:
public class Car {
private final String make;
private final String model;
private final int year;
private final String color;
private final boolean automatic;
private final int numDoors;
private final String features;
private Car(CarBuilder carBuilder) {
this.make = carBuilder.make;
this.model = carBuilder.model;
this.year = carBuilder.year;
this.color = carBuilder.color;
this.automatic = carBuilder.automatic;
this.numDoors = carBuilder.numDoors;
this.features = carBuilder.features;
}
// standard getters
}
This pattern is a powerful and flexible way to create objects, and it makes our code more readable, more maintainable, and less error-prone:
Car car = new Car.CarBuilder("Ford", "Focus", 2023).color("blue")
.automatic(true)
.features("abs, navi, charger, wifi, phone, satellite")
.build();
vehicleProcessor.processCar(car);
The main drawback of the Builder Pattern is that it requires the creation of a separate builder class for each class that uses this approach, which can lead to additional boilerplate code and complexity, mainly when dealing with a small number of arguments. Furthermore, implementing the Builder Pattern for large classes can be complex and may not be the most efficient solution for all use cases.
6. Summary
Let’s summarize the pros and cons of each of the best practices we’ve seen in this article:
Practice
Pros
Cons
Parameter Object
Encapsulates related parameters into a single object.
Requires creating a new class for each method.
Improves code readability and maintainability.
Can be overkill for methods with few parameters.
Easier to extend or modify without changing the method signature.
Java Bean
Encapsulates related parameters using a simple class.
Requires creating a new class for each method.
Provides getter and setter methods for easy access.
Can be verbose with lots of getter and setter methods.
Can be used as a form of documentation for parameters.
Not suitable for immutable objects.
Can set default values for parameters.
Needs to create getters/setters.
Can easily add or remove parameters without changing the method signature.
Java Varargs
Allows a variable number of arguments of the same type.
Only applicable to arguments of the same type.
Reduces the need for overloaded methods.
Can be less readable when dealing with many arguments, leading to performance issues with large numbers of arguments.
No need to create additional classes or methods.
Can be less type-safe and prone to runtime errors.
Builder Pattern
Allows step-by-step object construction.
Requires creating a separate builder class.
Improves code readability by using method chaining.
Can be verbose when dealing with a small number of args.
Supports optional parameters and default values.
Can be complex to implement for large classes.
Suitable for immutable objects.
Can be less performant than other alternatives.
7. Conclusion
As we’ve seen, passing many arguments to a Java method can be handled differently, and each approach has pros and cons. However, by following these best practices, we can improve the quality of our code.
As always, the complete code samples for this article can be found over on GitHub.