|
| |
| 3. 10. 4. instanceof操作符和类层次 |
|
|
|
class A {
int i, j;
}
class B {
int i, j;
}
class C extends A {
int k;
}
class D extends A {
int k;
}
class InstanceOf {
public static void main(String args[]) {
A a = new A();
B b = new B();
C c = new C();
D d = new D();
if (a instanceof A)
System.out.println("a is instance of A");
if (b instanceof B)
System.out.println("b is instance of B");
if (c instanceof C)
System.out.println("c is instance of C");
if (c instanceof A)
System.out.println("c can be cast to A");
if (a instanceof C)
System.out.println("a can be cast to C");
System.out.println();
A ob;
ob = d; // A reference to d
System.out.println("ob now refers to d");
if (ob instanceof D)
System.out.println("ob is instance of D");
System.out.println();
ob = c; // A reference to c
System.out.println("ob now refers to c");
if (ob instanceof D)
System.out.println("ob can be cast to D");
else
System.out.println("ob cannot be cast to D");
if (ob instanceof A)
System.out.println("ob can be cast to A");
System.out.println();
// all objects can be cast to Object
if (a instanceof Object)
System.out.println("a may be cast to Object");
if (b instanceof Object)
System.out.println("b may be cast to Object");
if (c instanceof Object)
System.out.println("c may be cast to Object");
if (d instanceof Object)
System.out.println("d may be cast to Object");
}
}
|
|
|