Clearing doubts about the builder pattern

Question

I am learning about the builder pattern, and so far I understood that, it is a great alternative to the commonly patterns used for initialization:

• Telescopi

Answer 1

The Builder pattern is useful to create immutable objects and avoid several constructors with optional parameters.

IMO using Builder pattern to build a POJO which can be updated using setters is useless. You only create an additional class.

Depending on the ORM framework used, it might not need the presence of setter method. But only assigning members values through reflection.

Product class:

public final class Product {
    private final String color;
    private final int price;

    public Product(Builder builder) {
        this.color = builder.getColor();
        this.price = builder.getPrice();
    }

    public String getColor() {
        return color;
    }

    public int getPrice() {
        return price;
    }

    public String toString() {
        return getColor() + "\n" + getPrice();
    }    
}

Builder class:

public final class Builder {

    private String color;
    private int price;

    public Builder() {
        // Assign any default values
    }

    public Builder color(String color) {        
        this.color = color;
        return this;
    }

    public Builder price(int price) {        
        this.price = price;
        return this;
    }

    protected String getColor() {
        return color;
    }

    protected int getPrice() {
        return price;
    }

    public Product build() {
        return new Product(this);
    }
}

Answer 2

Builder is about several things and you may want to utilize only one aspect: fluent API. You may attain the best fit for your needs by just changing your setters to return this instead of void. Then you can use the chained-setter idiom: return new MyBean().setCheese(cheese).setBacon(bacon);

On a side note, the term "POJO" does not mean the same as "JavaBean". In fact, sometimes these two terms are used as opposites. The point of a POJO is that it doesn't conform to anything else than being a Java object. It may use public variables, for example.