Consider the following example of builder pattern:
import java.util.Objects;
public class Vehicle {
private final String brand;
private final int wheels;
private final int doors;
private final int maxSpeed;
private Vehicle(Builder builder) {
this.brand = Objects.requireNonNull(builder.brand, "brand");
this.wheels = Objects.requireNonNull(builder.wheels, "wheels");
this.doors = Objects.requireNonNull(builder.doors, "doors");
this.maxSpeed = Objects.requireNonNull(builder.maxSpeed, "maxSpeed");
}
public static Builder builder() {
return new Builder();
}
public void display() {
System.out.println("brand = " + getBrand());
System.out.println("wheels = " + getWheels());
System.out.println("doors = " + getDoors());
System.out.println("maxSpeed = " + getMaxSpeed());
}
public String getBrand() {
return brand;
}
public int getWheels() {
return wheels;
}
public int getDoors() {
return doors;
}
public int getMaxSpeed() {
return maxSpeed;
}
public static class Builder {
private String brand;
private Integer wheels;
private Integer doors;
private Integer maxSpeed;
Builder() {
}
public Builder setBrand(String brand) {
this.brand = brand;
return this;
}
public Builder setWheels(int wheels) {
this.wheels = wheels;
return this;
}
public Builder setDoors(int doors) {
this.doors = doors;
return this;
}
public Builder setMaxSpeed(int maxSpeed) {
this.maxSpeed = maxSpeed;
return this;
}
public Builder of(Vehicle vehicle) {
this.brand = vehicle.brand;
this.wheels = vehicle.wheels;
this.doors = vehicle.doors;
this.maxSpeed = vehicle.maxSpeed;
return this;
}
public Vehicle build() {
return new Vehicle(this);
}
}
}
When we create an object of Vehicle
type, we have:
Vehicle vehicle = new Vehicle.Builder()
.setBrand("Mercedes")
.setWheels(4)
.setDoors(4)
.setMaxSpeed(250)
.build();
In order to achieve a similar fluent API, one can simply return this
in each setter of the class Vehicle
, e.g.:
public class Vehicle {
private final String brand;
private final int wheels;
private final int doors;
private final int maxSpeed;
private Vehicle(String brand, int wheels, int doors, int maxSpeed){
this.brand = brand;
this.wheels = wheels;
this.doors = doors;
this.maxSpeed = maxSpeed;
}
public Vehicle() {
}
public String getBrand() {
return brand;
}
public int getWheels() {
return wheels;
}
public int getDoors() {
return doors;
}
public int getMaxSpeed() {
return maxSpeed;
}
public Vehicle setBrand(String brand) {
this.brand = brand;
return this;
}
public Vehicle setWheels(int wheels) {
this.wheels = wheels;
return this;
}
public Vehicle setDoors(int doors) {
this.doors = doors;
return this;
}
public Vehicle setMaxSpeed(int maxSpeed) {
this.maxSpeed = maxSpeed;
return this;
}
public void display() {
System.out.println("brand = " + getBrand());
System.out.println("wheels = " + getWheels());
System.out.println("doors = " + getDoors());
System.out.println("maxSpeed = " + getMaxSpeed());
}
}
We can create an object of 'Vehicle' type by:
Vehicle vehicle = new Vehicle();
vehicle.setBrand("Mercedes")
.setDoors(4)
.setMaxSpeed(250);
In my opinion, the second approach produces less code than the conventional builder pattern. What do you guys think about that?
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