Question

我正在尝试理解下面的代码，其中返回类型被视为不兼容。

 return new PassLine(One, Two, roll);
 incompatible types: PassLine cannot be converted to TheDie

希望有人能说清楚，以便我可以继续。

我希望得到dieOne + dieTwo的总和。

public class PassLine {
    private int thePoint;

    private final TheDie dieOne;
    private final TheDie dieTwo;
    private final TheDie rollTheDie;

    public PassLine(TheDie dieOne, TheDie dieTwo, TheDie rollTheDie) {
        super();
        this.dieOne = dieOne;
        this.dieTwo = dieTwo;
        this.rollTheDie = rollTheDie;
    }

    public TheDie dieOne() {
        TheDie obj = new TheDie();
        obj.rollTheDie();
        return dieOne;
    }

    public TheDie dieTwo() {
        TheDie obj = new TheDie();
        obj.rollTheDie();
        return dieTwo;
    }

    public TheDie rollTheDie() {
        dieOne();
        dieTwo();
        return rollTheDie;
    }

        public PassLine passLine() {

    TheDie One = dieOne();
    TheDie Two = dieTwo();
    TheDie roll = rollTheDie();

    return new PassLine(One, Two, roll);
}

    public static void main(String[] args) {
        System.exit(0);
    }
}

来自 - 公共决赛班TheDie

    public int rollTheDie() {

    Random rand = new Random();
    oneDie = rand.nextInt(6) + 1;

    return oneDie;

    }

新的错误消息如下：

于：返回新的PassLine（一，二，滚动）;

错误：

     Incompatible Type: TheDiecannot be converted to String
     Incompatible Type: TheDiecannot be converted to String
     Introduce...
     May split declaration into a declaration and assignment 
     Flip operands of the binary operator

Answer 1

错误不能更清楚，

public TheDie PassLine() {

    TheDie One = dieOne();
    TheDie Two = dieTwo();
    TheDie roll = rollTheDie();

    return new PassLine(One, Two, roll);
}

您指定在返回TheDie对象时该方法应返回PassLine对象。

根据您的错误消息

不兼容的类型：PassLine无法转换为TheDie

两种类型都不兼容，请将方法更改为

public PassLine PassLine() {

    TheDie One = dieOne();
    TheDie Two = dieTwo();
    TheDie roll = rollTheDie();

    return new PassLine(One, Two, roll);
}

也许您真的想通过调用一个真正在新TheDie对象上返回TheDie的方法来返回PassLine。

Answer 2

方法PassLine（奇怪的名称，与类的名称相同...）被声明为返回TheDie对象，但返回PassLine对象，因此错误。< / p>

您必须将方法的返回类型更改为PassLine或返回TheDie对象。

你真的想拥有一个同名的方法吗？它不是一个编辑不好的构造函数吗？

请注意：Java命名约定是：

包名称和方法名称的lowerCamelCase
类和接口名称的UpperCamelCase

您的课程PassLine的方法为PassLine（应为passLine）

Answer 3

您有两种不同的类类型：TheDie和PassLine。假设TheDie不是一个从PassLine扩展的类，你将会有不兼容的类型，因为

public TheDie PassLine() {
        ...
        return new PassLine(One, Two, roll);
    }

方法标题指出您应该返回TheDie的对象。

Answer 4

在您的代码中：

public TheDie PassLine() {

TheDie One = dieOne();
TheDie Two = dieTwo();
TheDie roll = rollTheDie();

return new PassLine(One, Two, roll);
}

您正在尝试将PassLine作为TheDie返回。将public TheDie PassLine()更改为public PassLine PassLine()

Java - 了解私有最终自定义类型的返回类型

4 个答案: