英文:
Why can't I access the data field of Point2D in Java?
问题
我想使用Point2D创建一个包含100个随机点的数组。但为什么我无法访问其数据字段，而Point2D的数据字段是公共的？它显示“无法解析x，或者x不是一个字段”。
public static void main(String[] args) {
Point2D[] points = new Point2D.Double[100];
for (int i = 0; i < points.length; i++) {
points[i] = new Point2D.Double();
points[i].x = Math.random() * 100;
points[i].y = Math.random() * 100;
}
}
英文:
I want to create an array of 100 random points using Point2D. But why can't I access its data field while the data field of Point2D is public? It said "x cannot be resolved or not a field."
public static void main(String[] args) {
Point2D[] points = new Point2D.Double[100];
for (int i = 0; i < points.length; i++) {
points[i] = new Point2D.Double();
points[i].x = Math.random() * 100;
points[i].y = Math.random() * 100;
}
}
答案1
得分: 0
你可能想使用setLocation方法。错误信息只是说编译器不知道在类型为Point2D的对象上，.x应该表示什么。
英文:
You might want to use setLocation. The error-message just says that the compiler doesn't know what .x is supposed to mean on an object of type Point2D.
答案2
得分: 0
在你的代码中，points 的类型是 Point2D[]，因此 points[i] 的类型是 Point2D。Point2D 没有名为 x 或 y 的成员。在运行时，points[i] 的类恰好是 Point2D.Double，而这个类具有这样的成员，但这与编译器的分析无关。
你可以改为将 points 声明为
Point2D.Double[] points = new Point2D.Double[100];
或者你可以使用 Point2D.setLocation() 方法来代替直接赋值给成员变量，正如你的其他回答中已经建议的那样。
英文:
In your code, points has type Point2D[], therefore points[i] has type Point2D. Point2D does not have members named x or y. The fact that at runtime the class of points[i] happens to be Point2D.Double, which does have such members, is irrelevant to the compiler's analysis.
You could instead declare points as
Point2D.Double[] points = new Point2D.Double[100];
, or you could use Point2D.setLocation() instead of assigning to member variables, as your other answer already suggests.
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