builder.md

Builder

Description

Provide a way to create a complex object with different representation in a simplified manner

This design pattern helps to get rid of the "telescopic constructor"

Diagram

Code

Check code here

public class Item {

    private String name;
    private String description;

    public Item(String name, String description) {
        this.name = name;
        this.description = description;
    }
}

public class ItemBuilder {

    private String name;
    private String description;

    public ItemBuilder name(String name) {
        this.name = name;
        return this;
    }

    public ItemBuilder description(String description) {
        this.description = description;
        return this;
    }

    public Item build() {
        return new Item(name, description);
    }

}

To access the instance

Item item = new ItemBuilder()
        .name("item name")
        .description("item description")
        .build();

A simplified version with lombok

You can apply the builder design pattern by simply adding the lombok @Builder annotation on the class

@Builder
public class Item {
    private String name;
    private String description;
}

To access the instance

Item item = Item.builder()
        .name("item name")
        .description("item description")
        .build();

Use cases

• StringBuilder with the method append(String str) to concatenate strings