To access a method frm a class derived frm a base class with the same name

Question

Here' s an example:-
class TestA {
public void start() {
System.out.println("TestA");
class TestB extends TestA {
public void start() {
System.out.println("TestB");
}In main method I do this:-
TestA testA = new TestA();
TestB testB = new TestB();
((TestA)testB).start();Output :-
TestB.
Now when i define the method as static :-
class TestA {
public static void start() {
System.out.println("TestA");
class TestB extends TestA {
public static void start() {
System.out.println("TestB");
}Then output is :-
TestA.
Can anyone let me know that when i say ((TestA)testB).start(); i.e i am type casting TestB obect to it base call then TestA should be printed but it doesn't print but when i declare method as static is does print TestA.
Thanks,
Heena

Answer 1

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Secondly, when i say ((TestA).testB).start(); output is TestB. But when i define start() method as static output is TestA. I need clarity for the same.In the static case, all that the compiler is interested in is the class of the expression before the ".". Because you've put in an explicit cast the type of expression is assumed to be TestA the compiler doesn't know what kind of object will actually be referenced at runtime. In the static case which method is called is determined at compile time.
In the instance method case what determines the method called is determined the class of the actual, run time, value of the expression, and despite your cast, the actual value is still a reference to a TestB instance, so the TestB method is called. In the instance case which method called is determined at run time.