Question

我正在尝试有效的Java书并享受它。我读了Builder模式，我试着玩它。我有这样的代码（在Groovy中）：

public class Anto {
    public static void main(String[] args) {

            def testing = new Java.Builder(1).author("antoaravinth").build()
            println testing.author
        }
}

class Java {
    int version
    def author
    int release_number

    public static class Builder {
        int version

        def author = ""
        int release_number = 0

        public Builder(int version) {
            this.version = version
        }

        public Builder version(int version)
        {
            version = version
            return this
        }

        public Builder author(def author)
        {
            author = author
            return this
        }

        public Builder release_number(int release_number)
        {
            release_number = release_number
            return this
        }

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


        private Java(Builder builder) 
        {
            version = builder.version
            author = builder.author
            release_number = builder.release_number
        }

    }
}

但我得到这样的错误：

Caught: groovy.lang.GroovyRuntimeException: Could not find matching constructor for: Java(Java$Builder)
groovy.lang.GroovyRuntimeException: Could not find matching constructor for: Java(Java$Builder)
    at Java$Builder.build(Anto.groovy:43)
    at Java$Builder$build.call(Unknown Source)
    at Anto.main(Anto.groovy:4)

我不知道为什么会这样！哪里出错了？

Answer 1

这是您的build()方法：

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

查看你的Java类（不是Builder） - 它没有任何显式声明的构造函数，所以它唯一的构造函数是为你自动声明的public parameterless。 / p>

你需要移动它：

private Java(Builder builder) 
{
    version = builder.version
    author = builder.author
    release_number = builder.release_number
}

在Builder课程之外。（我有点惊讶Groovy之前没有抱怨，但我很确定这是问题......）

编辑：既然它没有抛出异常，请查看“setter”方法：

public Builder version(int version)
{
    version = version
    return this
}

version = version行没有做任何事情。您需要区分参数和字段，例如

public Builder version(int version)
{
    this.version = version
    return this
}

...或者给参数指定一个不同的名称，例如

public Builder version(int value)
{
    version = value
    return this
}

在我的Builder模式中找不到匹配的构造函数错误

1 个答案: