实现 Iterable 的通用类
我想要一个实现 T 类型的 Iterable（我们称之为 ImplIterable）的泛型类，它在某个类（不属于泛型类类型）上实现 Iterable 接口；例如：
public class ImplIterable <T> implements Iterable<A> {
private A[] tab;
public Iterator<A> iterator() {
return new ImplIterator();
}
// doesn't work - but compiles correctly.
private class ImplIterator implements Iterator<A> {
public boolean hasNext() { return true; }
public A next() { return null; }
public void remove() {}
}
}
其中 A 是某个类。现在，这段代码不会编译：
ImplIterable iable = new ImplIterable();
for (A a : iable) {
a.aStuff();
}
但这会：
Iterable<A> = new ImplIterable();
for (A a : iable) {
a.aStuff();
}
我不明白为什么后者不能编译，为什么我不能迭代 ImplIterable（如果它正确实现了 iterable）。我做错了什么/是否有解决此类问题的方法？
I want to have a generic class that implements Iterable (let's call it ImplIterable) of type T that implements an Iterable interface over some class (that isn't of the generic class type); for example:
public class ImplIterable <T> implements Iterable<A> {
private A[] tab;
public Iterator<A> iterator() {
return new ImplIterator();
}
// doesn't work - but compiles correctly.
private class ImplIterator implements Iterator<A> {
public boolean hasNext() { return true; }
public A next() { return null; }
public void remove() {}
}
}
Where A is some class. Now, this code won't compile:
ImplIterable iable = new ImplIterable();
for (A a : iable) {
a.aStuff();
}
But this will:
Iterable<A> = new ImplIterable();
for (A a : iable) {
a.aStuff();
}
I don't understand why the latter doesn't compile and why can't I iterate over ImplIterable if it properly implements iterable. Am I doing something wrong/is there some workaround for this type of problems?
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当您使用不带泛型参数的泛型类时，该类中的所有泛型都会被禁用。
由于
ImplIterable是泛型的，并且您将其用作非泛型类，因此它内部的泛型参数消失了，并且它变成了Iterable（非泛型）对象。When you use a generic class without a generic parameter, all generics in that class are disabled.
Since
ImplIterableis generic, and you're using it as a non-generic class, the generic parameters inside of it vanish, and it becomes anIterable(non-generic) ofObjects.