Overloading and Overriding

[Arnb Sen]

Why does this code compile ?

public class class1 {
public static void main(String args[]) {
System.out.println("main");
}

public void test(String name) {
System.out.println("test");
}

public void test(StringBuffer name){}
public void test(String name){}
}

[ November 26, 2005: Message edited by: Arnb Sen ]

[Ulf Dittmer]

It doesn't. You can't have two methods declarations with the same signature. You can however, as the class does, overload 'test' by methods with different signatures.

[Arnb Sen]

Thanks Ulf.


These are set of codes which I wrote. Some are overloading, some are overriding and some are simlpe hiding.

I have clasified them. Are they correct ?

FIRST CODE

class class2Base {
public void methodInBase(int i) {
System.out.println("methodInBase");
}
}
 
public class class2 extends class2Base {
public static void main(String args[]) {
System.out.println("main");
class2Base c2 = new class2Base();
c2.methodInBase(5);
}
public void methodInBase(int i, int j) {
System.out.println("Not In Base");
}
}
 

SECOND CODE

class class2Base {
public void methodInBase(int i) {
System.out.println("methodInBase");
}
}
 
public class class2 extends class2Base {
public static void main(String args[]) {
System.out.println("main");
class2Base c2 = new class2Base();
c2.methodInBase(5);
}
public int methodInBase(int i) {
System.out.println("Not In Base");
}
}
 

THIRD CODE

class class2Base {
public void methodInBase(int i) {
System.out.println("methodInBase");
}
}
 
public class class2 extends class2Base {
public static void main(String args[]) {
System.out.println("main");
class2Base c2 = new class2Base();
c2.methodInBase(5);
}
public int methodInBase(int i) {
System.out.println("Not In Base");
}
}
 

FOURTH CODE

class class2Base {
public void methodInBase(int i) {
System.out.println("methodInBase");
}
}
 
public class class2 extends class2Base {
public static void main(String args[]) {
System.out.println("main");
class2Base c2 = new class2Base();
c2.methodInBase(5);
}
public void methodInBase(int i) {
System.out.println("Not In Base");
}
}
 

FIFTH CODE

class class2Base {
public void methodInBase(int i) {
System.out.println("methodInBase");
}
}
 
public class class2 extends class2Base {
public static void main(String args[]) {
System.out.println("main");
class2Base c2 = new class2();
c2.methodInBase(5);
}
public void methodInBase(int i) {
System.out.println("Not In Base");
}
}
 

SIXTH CODE

class class2Base {
public void methodInBase(int i) {
System.out.println("methodInBase");
}
}
 
public class class2 extends class2Base {
public static void main(String args[]) {
System.out.println("main");
class2 c2 = new class2Base();
c2.methodInBase(5);
}
public void methodInBase(int i) {
System.out.println("Not In Base");
}
}

Categories : Overloading, Overriding, Hiding

1. FIRST CODE - Creating an instance of Base class in the subclass. Which cateory does this fall in ?
2. SECOND CODE - Is this Overriding ? Code does not compile. Method "methodInBase" has different return type in subclass as compared to that of the Base class.
3. THIRD CODE -
4. FOURTH CODE - This is Overriding
5. FIFTH CODE - This is Overriding as well
6. SIXTH CODE - This will not compile because sublass variable cannot reference an instance of Base class.

[Sowjanya Chowdary]

Arnb,

1. FIRST CODE - overloading
2. SECOND CODE - This is not a valid overriding or overloading. That is the reason for compilation error.
3. THIRD CODE - same as above
4. FOURTH CODE - This is Overriding.
5. FIFTH CODE - This is Overriding.
6. SIXTH CODE - This is also Overriding. But, compilation error because base class object can't be assigned to a subclass reference(class2 c2 = new class2Base() .
Hope this helps.

[Stuart Ash]

Originally posted by Arnb Sen:
Why does this code compile ?



[ November 26, 2005: Message edited by: Arnb Sen ]

What made you say it compiles??

[Arnb Sen]

Hi Amrutha,

Thanks a lot. Helps

Hi Stuart,

The code was slightly different when I was compiling in textpad and then to make it neater while posting, I modified some of the names.

When Ulf pointed out that it is not compiling, I cross-checked the code that I had and the one I posted and realised that while changing the names, I made an error.

[Stuart Ash]

Ah ok