java - 构建器模式(java)。为什么 Builder 类是公共(public)的？

Question

为什么我每次看到内部构建器类都是公共(public)静态的？不应该是私有(private)静态吗？也许我没有看到什么，但我会说它会更好。谁能给我解释一下吗？

@Getter @AllArgsConstructor @ToString
public class CarDto {

private final String make;
private final int seatCount;
private final String type;
private final CarDto carDto;

public static Builder builder(){
    return new Builder();
}


private static class Builder{
    private String make;
    private int seatCount;
    private String type;
    private CarDto carDto;


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

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

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

    public Builder carDto(CarDto carDto){
        this.carDto = carDto;
        return this;
    }

    public CarDto create(){
        return new CarDto(make, seatCount,type,carDto);
    }
}
}

Answer 1

Builder 必须是公共(public)的才能从其他类访问。尝试获取构建器，调用静态工厂方法 CarDto.builder() 否则 - 您将无法使用任何构建方法，例如 seatCount(), 。 .., create().