| 5. 22. 9. 转换 |
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- With objects, you can cast an instance of a subclass to its parent class.
- Casting an object to a parent class is called upcasting.
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Child child = new Child ();
Parent parent = child;
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To upcast a Child object, all you need to do is assign the object to a reference variable of type Parent.
The parent reference variable cannot access the members that are only available in Child. |
Because parent references an object of type Child, you can cast it back to Child.
It is called downcasting because you are casting an object to a class down the inheritance hierarchy.
Downcasting requires that you write the child type in brackets.
For example: |
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Child child2 = (Child) parent;
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