JDK 15 Sealed 类 - 如何跨包使用？

Question

我有一个简单的密封class,MyShape:

public sealed class MyShape permits MyCircle {

    private final int width;
    private final int height;

    public MyShape(int width, int height) {
        this.width = width;
        this.height = height;
    }

    public int width() {
        return width;
    }

    public int height() {
        return height;
    }
}

还有一个简单的子class, MyCircle:

public final class MyCircle extends MyShape {

    public MyCircle(int width) {
        super(width, width);
    }
}

当两个 class 都在同一个包中时，一切都可以编译和工作。如果我将 MyCircle 移动到子包中，则构建中断：java: class is not allowed to extend sealed class: org.example.MyShape.

根据 JDK 15 docs 我的理解是这应该有效。我错过了一步吗？

我已经 created a GitHub repo 如果你想试验的话。

Answer 1

如您链接的文档中所述：

JDK 15 Documentation

They must be in the same module as the sealed class (if the sealed class is in a named module) or in the same package (if the sealed class is in the unnamed module).

JDK 15 Sealed 类 - 如何跨包使用？

JDK 15 Sealed Classes - how to use across packages?

java

sealed-class

java-15

java-sealed-type