java构建器模式和变化的字段

Question

我很难弄清楚如何更改由构建器模式创建的对象中的某些字段:例如，这是一个类

public class Pizza {
  private int size;
  private boolean cheese;
  private boolean pepperoni;
  private boolean bacon;

  public static class Builder {
    //required
    private final int size;

    //optional
    private boolean cheese = false;
    private boolean pepperoni = false;
    private boolean bacon = false;

    public Builder(int size) {
      this.size = size;
    }

    public Builder cheese(boolean value) {
      cheese = value;
      return this;
    }

    public Builder pepperoni(boolean value) {
      pepperoni = value;
      return this;
    }

    public Builder bacon(boolean value) {
      bacon = value;
      return this;
    }

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

  private Pizza(Builder builder) {
    size = builder.size;
    cheese = builder.cheese;
    pepperoni = builder.pepperoni;
    bacon = builder.bacon;
  }
}

Pizza 对象是这样创建的:

Pizza pizza = new Pizza.Builder(12)
                       .cheese(true)
                       .pepperoni(true)
                       .bacon(true)
                       .build();

现在我想知道如何改变这个对象例如奶酪场要假？我没有 getter 和 setter，我知道我可以使用反射，但这会使代码更难阅读和理解。那么构建器模式对于非最终对象有用吗？

Answer 1

构建器模式通常适合创建不可变对象(immutable对象)，但它并不需要这样做。如果您希望能够在 build 之后更改值，则只需为此添加一个 setter 即可。