Type casting in Java allows an object to be treated as another type. There are two types of casting: implicit casting, which Java performs automatically when types are compatible in the class hierarchy, and explicit casting, which requires a cast operator inserted by the programmer. Explicit casting may be necessary to call methods of the target class when the object type is of a subclass within the hierarchy.

1. OBJECT TYPE
CASTING

2. Type Casting
 Converting an object of one class to an
object of another class is possible if the
object types are compatible.
 Java will perform some conversion
automatically. Such conversions are
known as implicit type casting.
 Conversions forced by the programmer is
known as explicit type casting.

3. Eg.,
PERSON
X
Y Z TEACHER STUDENT
Z1 Z2
UG_STUD PG_STUD
ENT ENT

4. Class definition
public Class X Class Y extends X {
{
public void F(); public void F();
public void F1(); public void F2a();
} }
// X is a super class of Y Class Z extends X
and Z which are sub {
classes. public void F();
public void F2b();
}

5. Cont.,
Class Z1 extends Z
{
public void F();
public void F3a();
} // Z1,Z2 are subclasses which is
derived from Z.
Class Z2 extends Z
{
public void F();
public void F3b();
}

6. Cont..
1. X x = new X(); //no casting required
2. Y y = new Y(); //no casting required
3. Z z = new Z(); //no casting required
4. X xy = new Y(); // compiles ok (up the
hierarchy)
5. X xz = new Z(); // compiles ok (up the
hierarchy)
6. Y yz = new Z();// incompatible type
(siblings)

7. Cont..
1. X x = new X(); //no casting required
2. Y y = new Y(); //no casting required
3. Z z = new Z(); //no casting required
4. X xy = new Y(); // compiles ok (up the
hierarchy)
5. X xz = new Z(); // compiles ok (up the
hierarchy)
6. Y yz = new Z();// incompatible type
(siblings)

8. Cont..
1. Y yz = new Z(); //incompatible type
(siblings)
2. Y y1 = new X(); //incompatible. X is not a
Y
3. Z z1 = new X(); //X is not a Z
4. X x1 = y; // compiles ok (y is subclass of X)
5. X x2 = z; // compiles ok (z is subclass of X)

9. Object type Casting
Y yx = (Y) x1; // compiles and runs ok (x1 is type Y)
Z zx = (Z) x2; // compiles and runs ok (x2 is type Z)
// X xy = new Y(); (declared earlier)
xy.F(); //calls method F() of class X
((Y)xy).F(); //explicitly type cast xy to
method call F() class Y
((Y)xy).F2a(); // call the method F2a()
from class Y

10. Object Type Casting.,
X xz1=new Z1();
((Z1)xz1).F();//calls method F() in class Z1
((Z1)xz1).F1();//calls method F1() in class X
((Z1)xz1).F2b();//calls method F2b() in class Z
((Z1)xz1).F3a();//calls method F3a() in class Z1

11. THANK YOU!