How can the Object class be a super class of subclasses?

Clash Royale CLAN TAG#URR8PPP

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Fact 1:

Java does not support multiple inheritance.

Fact 2:

Object is a superclass of all other classes

If I have a class Parent and a class Child which is inheriting the class Parent:

class Parent 



class Child extends Parent 

In this case, how will the class Child inherit the Object class, if Java does not support multiple inheritance?

How is the relationship between these three defined?

Option 1:

Option 2:

java oop inheritance multiple-inheritance

share|improve this question

edited Aug 31 at 14:46

Andrew Tobilko

20.4k83773

asked Aug 31 at 9:41

Abhishek Keshri

2,139422

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Object is the superclass of every class in Java.
  – deHaar
  Aug 31 at 9:43
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @Arvind multilevel inheritance and multiple inheritance are not the same things. Java supports the multilevel inheritance, but C++ does both.
  – Abhishek Keshri
  Aug 31 at 10:02
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  please don't post answers/solutions in questions but feel free to write a new answer instead and mark it as accepted if you may think that's the real solution to your problem. See stackoverflow.com/help/self-answer
  – fantaghirocco
  Aug 31 at 10:46
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AbhishekKeshri yes you can - just use the answer box below. All "self-answer" does is display an answer box on the question field. But do you need to post an answer at all? Seems like there is already a perfectly good answer, which you have accepted.
  – Ant P
  Aug 31 at 11:53
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AntP I will remove the Solution part. Your argument makes sense.
  – Abhishek Keshri
  Aug 31 at 12:02
  

  
  
  
  

 | 
show 16 more comments

up vote
7
down vote

favorite

1

Fact 1:

Java does not support multiple inheritance.

Fact 2:

Object is a superclass of all other classes

If I have a class Parent and a class Child which is inheriting the class Parent:

class Parent 



class Child extends Parent 

In this case, how will the class Child inherit the Object class, if Java does not support multiple inheritance?

How is the relationship between these three defined?

Option 1:

Option 2:

java oop inheritance multiple-inheritance

share|improve this question

edited Aug 31 at 14:46

Andrew Tobilko

20.4k83773

asked Aug 31 at 9:41

Abhishek Keshri

2,139422

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Object is the superclass of every class in Java.
  – deHaar
  Aug 31 at 9:43
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @Arvind multilevel inheritance and multiple inheritance are not the same things. Java supports the multilevel inheritance, but C++ does both.
  – Abhishek Keshri
  Aug 31 at 10:02
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  please don't post answers/solutions in questions but feel free to write a new answer instead and mark it as accepted if you may think that's the real solution to your problem. See stackoverflow.com/help/self-answer
  – fantaghirocco
  Aug 31 at 10:46
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AbhishekKeshri yes you can - just use the answer box below. All "self-answer" does is display an answer box on the question field. But do you need to post an answer at all? Seems like there is already a perfectly good answer, which you have accepted.
  – Ant P
  Aug 31 at 11:53
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AntP I will remove the Solution part. Your argument makes sense.
  – Abhishek Keshri
  Aug 31 at 12:02
  

  
  
  
  

 | 
show 16 more comments

up vote
7
down vote

favorite

1

up vote
7
down vote

favorite

1

1

Fact 1:

Java does not support multiple inheritance.

Fact 2:

Object is a superclass of all other classes

If I have a class Parent and a class Child which is inheriting the class Parent:

class Parent 



class Child extends Parent 

In this case, how will the class Child inherit the Object class, if Java does not support multiple inheritance?

How is the relationship between these three defined?

Option 1:

Option 2:

java oop inheritance multiple-inheritance

share|improve this question

edited Aug 31 at 14:46

Andrew Tobilko

20.4k83773

asked Aug 31 at 9:41

Abhishek Keshri

2,139422

Fact 1:

Java does not support multiple inheritance.

Fact 2:

Object is a superclass of all other classes

If I have a class Parent and a class Child which is inheriting the class Parent:

class Parent 



class Child extends Parent 

In this case, how will the class Child inherit the Object class, if Java does not support multiple inheritance?

How is the relationship between these three defined?

Option 1:

Option 2:

java oop inheritance multiple-inheritance

share|improve this question

edited Aug 31 at 14:46

Andrew Tobilko

20.4k83773

asked Aug 31 at 9:41

Abhishek Keshri

2,139422

share|improve this question

share|improve this question

edited Aug 31 at 14:46

Andrew Tobilko

20.4k83773

edited Aug 31 at 14:46

Andrew Tobilko

20.4k83773

edited Aug 31 at 14:46

Andrew Tobilko

20.4k83773

20.4k83773

asked Aug 31 at 9:41

Abhishek Keshri

2,139422

asked Aug 31 at 9:41

Abhishek Keshri

2,139422

asked Aug 31 at 9:41

Abhishek Keshri

2,139422

2,139422

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Object is the superclass of every class in Java.
  – deHaar
  Aug 31 at 9:43
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @Arvind multilevel inheritance and multiple inheritance are not the same things. Java supports the multilevel inheritance, but C++ does both.
  – Abhishek Keshri
  Aug 31 at 10:02
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  please don't post answers/solutions in questions but feel free to write a new answer instead and mark it as accepted if you may think that's the real solution to your problem. See stackoverflow.com/help/self-answer
  – fantaghirocco
  Aug 31 at 10:46
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AbhishekKeshri yes you can - just use the answer box below. All "self-answer" does is display an answer box on the question field. But do you need to post an answer at all? Seems like there is already a perfectly good answer, which you have accepted.
  – Ant P
  Aug 31 at 11:53
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AntP I will remove the Solution part. Your argument makes sense.
  – Abhishek Keshri
  Aug 31 at 12:02
  

  
  
  
  

 | 
show 16 more comments

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Object is the superclass of every class in Java.
  – deHaar
  Aug 31 at 9:43
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @Arvind multilevel inheritance and multiple inheritance are not the same things. Java supports the multilevel inheritance, but C++ does both.
  – Abhishek Keshri
  Aug 31 at 10:02
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  please don't post answers/solutions in questions but feel free to write a new answer instead and mark it as accepted if you may think that's the real solution to your problem. See stackoverflow.com/help/self-answer
  – fantaghirocco
  Aug 31 at 10:46
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AbhishekKeshri yes you can - just use the answer box below. All "self-answer" does is display an answer box on the question field. But do you need to post an answer at all? Seems like there is already a perfectly good answer, which you have accepted.
  – Ant P
  Aug 31 at 11:53
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AntP I will remove the Solution part. Your argument makes sense.
  – Abhishek Keshri
  Aug 31 at 12:02
  

  
  
  
  

Object is the superclass of every class in Java.
– deHaar
Aug 31 at 9:43

Object is the superclass of every class in Java.
– deHaar
Aug 31 at 9:43

1

1

@Arvind multilevel inheritance and multiple inheritance are not the same things. Java supports the multilevel inheritance, but C++ does both.
– Abhishek Keshri
Aug 31 at 10:02

@Arvind multilevel inheritance and multiple inheritance are not the same things. Java supports the multilevel inheritance, but C++ does both.
– Abhishek Keshri
Aug 31 at 10:02

1

1

please don't post answers/solutions in questions but feel free to write a new answer instead and mark it as accepted if you may think that's the real solution to your problem. See stackoverflow.com/help/self-answer
– fantaghirocco
Aug 31 at 10:46

please don't post answers/solutions in questions but feel free to write a new answer instead and mark it as accepted if you may think that's the real solution to your problem. See stackoverflow.com/help/self-answer
– fantaghirocco
Aug 31 at 10:46

1

1

@AbhishekKeshri yes you can - just use the answer box below. All "self-answer" does is display an answer box on the question field. But do you need to post an answer at all? Seems like there is already a perfectly good answer, which you have accepted.
– Ant P
Aug 31 at 11:53

@AbhishekKeshri yes you can - just use the answer box below. All "self-answer" does is display an answer box on the question field. But do you need to post an answer at all? Seems like there is already a perfectly good answer, which you have accepted.
– Ant P
Aug 31 at 11:53

1

1

@AntP I will remove the Solution part. Your argument makes sense.
– Abhishek Keshri
Aug 31 at 12:02

@AntP I will remove the Solution part. Your argument makes sense.
– Abhishek Keshri
Aug 31 at 12:02

 | 
show 16 more comments

10 Answers
10

active

oldest

votes

up vote
20
down vote



accepted

It's Option 2. If you define a superclass, that will be the immediate superclass of your class. If you don't define one, Object will be the immediate superclass.

class Parent 



class Child extends Parent 

is equivalent to

class Parent extends Object 



class Child extends Parent 

So, while Object is the superclass of all classes, there might be some steps in the class hierarchy before you get to Object. It's not the immediate superclass of all classes.

share|improve this answer

edited Aug 31 at 9:47

answered Aug 31 at 9:43

Max Vollmer

4,93731233

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Won't class Child also inherit Object? Won't it be class Child extends Parent, Object (if it's possible internally somehow!!!)?
  – Abhishek Keshri
  Aug 31 at 9:46
  

  
  
  
  


• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  @AbhishekKeshri No. Child inherits Object through Parent.
  – Max Vollmer
  Aug 31 at 9:47
  

  
  
  
  

add a comment | 

up vote
5
down vote

Object might not be a direct parent, but it's always a super parent.

Child extends Parent
Parent extends Object

 |
 V

Child [indirectly] extends Object

share|improve this answer

edited Aug 31 at 9:50

answered Aug 31 at 9:46

Andrew Tobilko

20.4k83773

• 
  
  
  

  
  

  
  
  
  
  
  

  
  @AbhishekKeshri if the scenario 1 were correct, we would encounter the problem of choosing methods for the subclass (since both Object and Parent extends Object have the same set of methods including equals, hashCode, etc.)
  – Andrew Tobilko
  Aug 31 at 9:59
  

  
  
  
  

add a comment | 

up vote
4
down vote

The JavaDoc says:

Class Object is the root of the class hierarchy. ...

If a class does not extend any other class by decalring it using the keyword extends it extends though implicit from Object.

See the Example 8.1.4-1 "Direct Superclasses and Subclasses" in the JLS, chapter 8.1.4

It shows that a class Point int x, y; "is a direct subclass of Object"

Further the JLS says:

The subclass relationship is the transitive closure of the direct
subclass relationship.

Therefore Object is the superclass of all classes.

Going on with the example a class ColoredPoint extends Point int color; "is a direct subclass of class Point.". By the transitive relationship it's a (non-direct) subclass of class Object.

Summarizing: Object is either the direct superclass or by transitive relationship the last superclass of any other class.

Answering your question:

The class Parent corresponds to the class Point and the class Child to the class ColoredPoint of the example. Only Option 2 shows this relation.

share|improve this answer

edited Aug 31 at 10:40

answered Aug 31 at 9:52

LuCio

1,257515

add a comment | 

up vote
3
down vote

Well it is an interesting discussion. I think it will be option no 2. As if you try the below code .

public static void main(String args)
 Parent p=new Parent();
 Class c= p.getClass();

 Child child =new Child();
 Class c1= child.getClass();
 System.out.println(c.getSuperclass());
 System.out.println(c1.getSuperclass());

 

You will get output as :

class java.lang.Object 
class Parent

share|improve this answer

edited Aug 31 at 10:02

answered Aug 31 at 9:51

codeLover

1,605314

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using the following code solved my doubt: Class child_super = c1.getSuperclass(); System.out.println(child_super.getSuperclass());
  – Abhishek Keshri
  Aug 31 at 9:59
  

  
  
  
  

add a comment | 

up vote
1
down vote

The right answer is Option 2. Any Java class inherit all parents for their parents. In other words.

Class A extends Class B
Class B extends Class C
Class C extends Class D

Class X extends A -> it means that A inherit all protected/package/public fields from B,C and D.

In your example, Class Child inherit Parent properties but also Object properties in transitive mode.

share|improve this answer

answered Aug 31 at 9:51

admoca60

10112

add a comment | 

up vote
1
down vote

From Class Object

public class Object

Class Object is the root of the class hierarchy.

Every class has Object as a superclass.
All objects, including arrays, implement the methods of this class.

This means that every Java class has Object as root in the hierarchy, not necessarily as its immediate parent.

share|improve this answer

answered Aug 31 at 9:53

fantaghirocco

3,57952436

add a comment | 

up vote
1
down vote

No multiple inheritance means in Java a class extends only 1 class; has one immediate base class. Indirectly a class can have many ancestors: Child has Parent and Object as ancestor "super" classes.

Object --> Parent --> Child
 --> OtherChild

Relation: 1 --> N

The reason for avoiding multiple inheritance like in C++, was the ambiguity involved:

Pseudo code assuming multiple inheritance:

class A : Comparable
class B : Comparable

class Child : A, B 

 @Override A? B?
 int compareTo(Child rhs) ... super.compareTo ? ... 


A a = new Child();
B b = new Child();
a.compareTo(b);

share|improve this answer

answered Aug 31 at 9:56

Joop Eggen

73.1k65399

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  why should we care about which method to override if the signatures are identical? Overriding just implies that we are not satisfied with parents' behaviour and want to implement ours. The problem is, rather, what happens when we call child.compareTo(anotherChild) without overriding (which method are we going to invoke?)
  – Andrew Tobilko
  Aug 31 at 10:15
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AndrewTobilko well said; compareTo(a); compareTo(b), compareTo(child); actually I did not want to say anything about multiple inheritance (and interfaces) as that would be out of scope of the question. Just that multiple inheritance is not having an ancestral line; rather that single inheritance means having one (code bearing) parent per class. I also did not treat default methods in interfaces.
  – Joop Eggen
  Aug 31 at 10:30
  

  
  
  
  

add a comment | 

up vote
1
down vote

First of all, using Java 8, it is possible to accomplish Multiple inheritance using Default methods of interfaces.

Secondly, your understanding regarding Object class is correctly represented in 'Option 2'.

However, it is not multiple inheritance, rather multilevel inheritance. 'Option 1' is multiple inheritance.

Please check this link to read more about them.

share|improve this answer

answered Aug 31 at 10:07

Shashank Singh

164

add a comment | 

up vote
0
down vote

Option 2, as every object derives Object.class methods

share|improve this answer

answered Aug 31 at 9:43

Alexander Khlystov

12

add a comment | 

up vote
0
down vote

option 2.Object is a superclass of all other classes,but Object may not a dirrect superclass of a classe.

share|improve this answer

answered Aug 31 at 9:45

zzcron toby

63

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10 Answers
10

active

oldest

votes

10 Answers
10

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
20
down vote



accepted

It's Option 2. If you define a superclass, that will be the immediate superclass of your class. If you don't define one, Object will be the immediate superclass.

class Parent 



class Child extends Parent 

is equivalent to

class Parent extends Object 



class Child extends Parent 

So, while Object is the superclass of all classes, there might be some steps in the class hierarchy before you get to Object. It's not the immediate superclass of all classes.

share|improve this answer

edited Aug 31 at 9:47

answered Aug 31 at 9:43

Max Vollmer

4,93731233

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Won't class Child also inherit Object? Won't it be class Child extends Parent, Object (if it's possible internally somehow!!!)?
  – Abhishek Keshri
  Aug 31 at 9:46
  

  
  
  
  


• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  @AbhishekKeshri No. Child inherits Object through Parent.
  – Max Vollmer
  Aug 31 at 9:47
  

  
  
  
  

add a comment | 

up vote
20
down vote



accepted

It's Option 2. If you define a superclass, that will be the immediate superclass of your class. If you don't define one, Object will be the immediate superclass.

class Parent 



class Child extends Parent 

is equivalent to

class Parent extends Object 



class Child extends Parent 

So, while Object is the superclass of all classes, there might be some steps in the class hierarchy before you get to Object. It's not the immediate superclass of all classes.

share|improve this answer

edited Aug 31 at 9:47

answered Aug 31 at 9:43

Max Vollmer

4,93731233

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Won't class Child also inherit Object? Won't it be class Child extends Parent, Object (if it's possible internally somehow!!!)?
  – Abhishek Keshri
  Aug 31 at 9:46
  

  
  
  
  


• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  @AbhishekKeshri No. Child inherits Object through Parent.
  – Max Vollmer
  Aug 31 at 9:47
  

  
  
  
  

add a comment | 

up vote
20
down vote



accepted

up vote
20
down vote



accepted

It's Option 2. If you define a superclass, that will be the immediate superclass of your class. If you don't define one, Object will be the immediate superclass.

class Parent 



class Child extends Parent 

is equivalent to

class Parent extends Object 



class Child extends Parent 

So, while Object is the superclass of all classes, there might be some steps in the class hierarchy before you get to Object. It's not the immediate superclass of all classes.

share|improve this answer

edited Aug 31 at 9:47

answered Aug 31 at 9:43

Max Vollmer

4,93731233

It's Option 2. If you define a superclass, that will be the immediate superclass of your class. If you don't define one, Object will be the immediate superclass.

class Parent 



class Child extends Parent 

is equivalent to

class Parent extends Object 



class Child extends Parent 

So, while Object is the superclass of all classes, there might be some steps in the class hierarchy before you get to Object. It's not the immediate superclass of all classes.

share|improve this answer

edited Aug 31 at 9:47

answered Aug 31 at 9:43

Max Vollmer

4,93731233

share|improve this answer

share|improve this answer

edited Aug 31 at 9:47

edited Aug 31 at 9:47

edited Aug 31 at 9:47

answered Aug 31 at 9:43

Max Vollmer

4,93731233

answered Aug 31 at 9:43

Max Vollmer

4,93731233

answered Aug 31 at 9:43

Max Vollmer

4,93731233

4,93731233

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Won't class Child also inherit Object? Won't it be class Child extends Parent, Object (if it's possible internally somehow!!!)?
  – Abhishek Keshri
  Aug 31 at 9:46
  

  
  
  
  


• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  @AbhishekKeshri No. Child inherits Object through Parent.
  – Max Vollmer
  Aug 31 at 9:47
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Won't class Child also inherit Object? Won't it be class Child extends Parent, Object (if it's possible internally somehow!!!)?
  – Abhishek Keshri
  Aug 31 at 9:46
  

  
  
  
  


• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  @AbhishekKeshri No. Child inherits Object through Parent.
  – Max Vollmer
  Aug 31 at 9:47
  

  
  
  
  

Won't class Child also inherit Object? Won't it be class Child extends Parent, Object (if it's possible internally somehow!!!)?
– Abhishek Keshri
Aug 31 at 9:46

Won't class Child also inherit Object? Won't it be class Child extends Parent, Object (if it's possible internally somehow!!!)?
– Abhishek Keshri
Aug 31 at 9:46

6

6

@AbhishekKeshri No. Child inherits Object through Parent.
– Max Vollmer
Aug 31 at 9:47

@AbhishekKeshri No. Child inherits Object through Parent.
– Max Vollmer
Aug 31 at 9:47

add a comment | 

up vote
5
down vote

Object might not be a direct parent, but it's always a super parent.

Child extends Parent
Parent extends Object

 |
 V

Child [indirectly] extends Object

share|improve this answer

edited Aug 31 at 9:50

answered Aug 31 at 9:46

Andrew Tobilko

20.4k83773

• 
  
  
  

  
  

  
  
  
  
  
  

  
  @AbhishekKeshri if the scenario 1 were correct, we would encounter the problem of choosing methods for the subclass (since both Object and Parent extends Object have the same set of methods including equals, hashCode, etc.)
  – Andrew Tobilko
  Aug 31 at 9:59
  

  
  
  
  

add a comment | 

up vote
5
down vote

Object might not be a direct parent, but it's always a super parent.

Child extends Parent
Parent extends Object

 |
 V

Child [indirectly] extends Object

share|improve this answer

edited Aug 31 at 9:50

answered Aug 31 at 9:46

Andrew Tobilko

20.4k83773

• 
  
  
  

  
  

  
  
  
  
  
  

  
  @AbhishekKeshri if the scenario 1 were correct, we would encounter the problem of choosing methods for the subclass (since both Object and Parent extends Object have the same set of methods including equals, hashCode, etc.)
  – Andrew Tobilko
  Aug 31 at 9:59
  

  
  
  
  

add a comment | 

up vote
5
down vote

up vote
5
down vote

Object might not be a direct parent, but it's always a super parent.

Child extends Parent
Parent extends Object

 |
 V

Child [indirectly] extends Object

share|improve this answer

edited Aug 31 at 9:50

answered Aug 31 at 9:46

Andrew Tobilko

20.4k83773

Object might not be a direct parent, but it's always a super parent.

Child extends Parent
Parent extends Object

 |
 V

Child [indirectly] extends Object

share|improve this answer

edited Aug 31 at 9:50

answered Aug 31 at 9:46

Andrew Tobilko

20.4k83773

share|improve this answer

share|improve this answer

edited Aug 31 at 9:50

edited Aug 31 at 9:50

edited Aug 31 at 9:50

answered Aug 31 at 9:46

Andrew Tobilko

20.4k83773

answered Aug 31 at 9:46

Andrew Tobilko

20.4k83773

answered Aug 31 at 9:46

Andrew Tobilko

20.4k83773

20.4k83773

• 
  
  
  

  
  

  
  
  
  
  
  

  
  @AbhishekKeshri if the scenario 1 were correct, we would encounter the problem of choosing methods for the subclass (since both Object and Parent extends Object have the same set of methods including equals, hashCode, etc.)
  – Andrew Tobilko
  Aug 31 at 9:59
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  @AbhishekKeshri if the scenario 1 were correct, we would encounter the problem of choosing methods for the subclass (since both Object and Parent extends Object have the same set of methods including equals, hashCode, etc.)
  – Andrew Tobilko
  Aug 31 at 9:59
  

  
  
  
  

@AbhishekKeshri if the scenario 1 were correct, we would encounter the problem of choosing methods for the subclass (since both Object and Parent extends Object have the same set of methods including equals, hashCode, etc.)
– Andrew Tobilko
Aug 31 at 9:59

@AbhishekKeshri if the scenario 1 were correct, we would encounter the problem of choosing methods for the subclass (since both Object and Parent extends Object have the same set of methods including equals, hashCode, etc.)
– Andrew Tobilko
Aug 31 at 9:59

add a comment | 

up vote
4
down vote

The JavaDoc says:

Class Object is the root of the class hierarchy. ...

If a class does not extend any other class by decalring it using the keyword extends it extends though implicit from Object.

See the Example 8.1.4-1 "Direct Superclasses and Subclasses" in the JLS, chapter 8.1.4

It shows that a class Point int x, y; "is a direct subclass of Object"

Further the JLS says:

The subclass relationship is the transitive closure of the direct
subclass relationship.

Therefore Object is the superclass of all classes.

Going on with the example a class ColoredPoint extends Point int color; "is a direct subclass of class Point.". By the transitive relationship it's a (non-direct) subclass of class Object.

Summarizing: Object is either the direct superclass or by transitive relationship the last superclass of any other class.

Answering your question:

The class Parent corresponds to the class Point and the class Child to the class ColoredPoint of the example. Only Option 2 shows this relation.

share|improve this answer

edited Aug 31 at 10:40

answered Aug 31 at 9:52

LuCio

1,257515

add a comment | 

up vote
4
down vote

The JavaDoc says:

Class Object is the root of the class hierarchy. ...

If a class does not extend any other class by decalring it using the keyword extends it extends though implicit from Object.

See the Example 8.1.4-1 "Direct Superclasses and Subclasses" in the JLS, chapter 8.1.4

It shows that a class Point int x, y; "is a direct subclass of Object"

Further the JLS says:

The subclass relationship is the transitive closure of the direct
subclass relationship.

Therefore Object is the superclass of all classes.

Going on with the example a class ColoredPoint extends Point int color; "is a direct subclass of class Point.". By the transitive relationship it's a (non-direct) subclass of class Object.

Summarizing: Object is either the direct superclass or by transitive relationship the last superclass of any other class.

Answering your question:

The class Parent corresponds to the class Point and the class Child to the class ColoredPoint of the example. Only Option 2 shows this relation.

share|improve this answer

edited Aug 31 at 10:40

answered Aug 31 at 9:52

LuCio

1,257515

add a comment | 

up vote
4
down vote

up vote
4
down vote

The JavaDoc says:

Class Object is the root of the class hierarchy. ...

If a class does not extend any other class by decalring it using the keyword extends it extends though implicit from Object.

See the Example 8.1.4-1 "Direct Superclasses and Subclasses" in the JLS, chapter 8.1.4

It shows that a class Point int x, y; "is a direct subclass of Object"

Further the JLS says:

The subclass relationship is the transitive closure of the direct
subclass relationship.

Therefore Object is the superclass of all classes.

Going on with the example a class ColoredPoint extends Point int color; "is a direct subclass of class Point.". By the transitive relationship it's a (non-direct) subclass of class Object.

Summarizing: Object is either the direct superclass or by transitive relationship the last superclass of any other class.

Answering your question:

The class Parent corresponds to the class Point and the class Child to the class ColoredPoint of the example. Only Option 2 shows this relation.

share|improve this answer

edited Aug 31 at 10:40

answered Aug 31 at 9:52

LuCio

1,257515

The JavaDoc says:

Class Object is the root of the class hierarchy. ...

If a class does not extend any other class by decalring it using the keyword extends it extends though implicit from Object.

See the Example 8.1.4-1 "Direct Superclasses and Subclasses" in the JLS, chapter 8.1.4

It shows that a class Point int x, y; "is a direct subclass of Object"

Further the JLS says:

The subclass relationship is the transitive closure of the direct
subclass relationship.

Therefore Object is the superclass of all classes.

Going on with the example a class ColoredPoint extends Point int color; "is a direct subclass of class Point.". By the transitive relationship it's a (non-direct) subclass of class Object.

Summarizing: Object is either the direct superclass or by transitive relationship the last superclass of any other class.

Answering your question:

The class Parent corresponds to the class Point and the class Child to the class ColoredPoint of the example. Only Option 2 shows this relation.

share|improve this answer

edited Aug 31 at 10:40

answered Aug 31 at 9:52

LuCio

1,257515

share|improve this answer

share|improve this answer

edited Aug 31 at 10:40

edited Aug 31 at 10:40

edited Aug 31 at 10:40

answered Aug 31 at 9:52

LuCio

1,257515

answered Aug 31 at 9:52

LuCio

1,257515

answered Aug 31 at 9:52

LuCio

1,257515

1,257515

add a comment | 

add a comment | 

up vote
3
down vote

Well it is an interesting discussion. I think it will be option no 2. As if you try the below code .

public static void main(String args)
 Parent p=new Parent();
 Class c= p.getClass();

 Child child =new Child();
 Class c1= child.getClass();
 System.out.println(c.getSuperclass());
 System.out.println(c1.getSuperclass());

 

You will get output as :

class java.lang.Object 
class Parent

share|improve this answer

edited Aug 31 at 10:02

answered Aug 31 at 9:51

codeLover

1,605314

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using the following code solved my doubt: Class child_super = c1.getSuperclass(); System.out.println(child_super.getSuperclass());
  – Abhishek Keshri
  Aug 31 at 9:59
  

  
  
  
  

add a comment | 

up vote
3
down vote

Well it is an interesting discussion. I think it will be option no 2. As if you try the below code .

public static void main(String args)
 Parent p=new Parent();
 Class c= p.getClass();

 Child child =new Child();
 Class c1= child.getClass();
 System.out.println(c.getSuperclass());
 System.out.println(c1.getSuperclass());

 

You will get output as :

class java.lang.Object 
class Parent

share|improve this answer

edited Aug 31 at 10:02

answered Aug 31 at 9:51

codeLover

1,605314

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using the following code solved my doubt: Class child_super = c1.getSuperclass(); System.out.println(child_super.getSuperclass());
  – Abhishek Keshri
  Aug 31 at 9:59
  

  
  
  
  

add a comment | 

up vote
3
down vote

up vote
3
down vote

Well it is an interesting discussion. I think it will be option no 2. As if you try the below code .

public static void main(String args)
 Parent p=new Parent();
 Class c= p.getClass();

 Child child =new Child();
 Class c1= child.getClass();
 System.out.println(c.getSuperclass());
 System.out.println(c1.getSuperclass());

 

You will get output as :

class java.lang.Object 
class Parent

share|improve this answer

edited Aug 31 at 10:02

answered Aug 31 at 9:51

codeLover

1,605314

Well it is an interesting discussion. I think it will be option no 2. As if you try the below code .

public static void main(String args)
 Parent p=new Parent();
 Class c= p.getClass();

 Child child =new Child();
 Class c1= child.getClass();
 System.out.println(c.getSuperclass());
 System.out.println(c1.getSuperclass());

 

You will get output as :

class java.lang.Object 
class Parent

share|improve this answer

edited Aug 31 at 10:02

answered Aug 31 at 9:51

codeLover

1,605314

share|improve this answer

share|improve this answer

edited Aug 31 at 10:02

edited Aug 31 at 10:02

edited Aug 31 at 10:02

answered Aug 31 at 9:51

codeLover

1,605314

answered Aug 31 at 9:51

codeLover

1,605314

answered Aug 31 at 9:51

codeLover

1,605314

1,605314

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using the following code solved my doubt: Class child_super = c1.getSuperclass(); System.out.println(child_super.getSuperclass());
  – Abhishek Keshri
  Aug 31 at 9:59
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  using the following code solved my doubt: Class child_super = c1.getSuperclass(); System.out.println(child_super.getSuperclass());
  – Abhishek Keshri
  Aug 31 at 9:59
  

  
  
  
  

using the following code solved my doubt: Class child_super = c1.getSuperclass(); System.out.println(child_super.getSuperclass());
– Abhishek Keshri
Aug 31 at 9:59

using the following code solved my doubt: Class child_super = c1.getSuperclass(); System.out.println(child_super.getSuperclass());
– Abhishek Keshri
Aug 31 at 9:59

add a comment | 

up vote
1
down vote

The right answer is Option 2. Any Java class inherit all parents for their parents. In other words.

Class A extends Class B
Class B extends Class C
Class C extends Class D

Class X extends A -> it means that A inherit all protected/package/public fields from B,C and D.

In your example, Class Child inherit Parent properties but also Object properties in transitive mode.

share|improve this answer

answered Aug 31 at 9:51

admoca60

10112

add a comment | 

up vote
1
down vote

The right answer is Option 2. Any Java class inherit all parents for their parents. In other words.

Class A extends Class B
Class B extends Class C
Class C extends Class D

Class X extends A -> it means that A inherit all protected/package/public fields from B,C and D.

In your example, Class Child inherit Parent properties but also Object properties in transitive mode.

share|improve this answer

answered Aug 31 at 9:51

admoca60

10112

add a comment | 

up vote
1
down vote

up vote
1
down vote

The right answer is Option 2. Any Java class inherit all parents for their parents. In other words.

Class A extends Class B
Class B extends Class C
Class C extends Class D

Class X extends A -> it means that A inherit all protected/package/public fields from B,C and D.

In your example, Class Child inherit Parent properties but also Object properties in transitive mode.

share|improve this answer

answered Aug 31 at 9:51

admoca60

10112

The right answer is Option 2. Any Java class inherit all parents for their parents. In other words.

Class A extends Class B
Class B extends Class C
Class C extends Class D

Class X extends A -> it means that A inherit all protected/package/public fields from B,C and D.

In your example, Class Child inherit Parent properties but also Object properties in transitive mode.

share|improve this answer

answered Aug 31 at 9:51

admoca60

10112

share|improve this answer

share|improve this answer

answered Aug 31 at 9:51

admoca60

10112

answered Aug 31 at 9:51

admoca60

10112

answered Aug 31 at 9:51

admoca60

10112

10112

add a comment | 

add a comment | 

up vote
1
down vote

From Class Object

public class Object

Class Object is the root of the class hierarchy.

Every class has Object as a superclass.
All objects, including arrays, implement the methods of this class.

This means that every Java class has Object as root in the hierarchy, not necessarily as its immediate parent.

share|improve this answer

answered Aug 31 at 9:53

fantaghirocco

3,57952436

add a comment | 

up vote
1
down vote

From Class Object

public class Object

Class Object is the root of the class hierarchy.

Every class has Object as a superclass.
All objects, including arrays, implement the methods of this class.

This means that every Java class has Object as root in the hierarchy, not necessarily as its immediate parent.

share|improve this answer

answered Aug 31 at 9:53

fantaghirocco

3,57952436

add a comment | 

up vote
1
down vote

up vote
1
down vote

From Class Object

public class Object

Class Object is the root of the class hierarchy.

Every class has Object as a superclass.
All objects, including arrays, implement the methods of this class.

This means that every Java class has Object as root in the hierarchy, not necessarily as its immediate parent.

share|improve this answer

answered Aug 31 at 9:53

fantaghirocco

3,57952436

From Class Object

public class Object

Class Object is the root of the class hierarchy.

Every class has Object as a superclass.
All objects, including arrays, implement the methods of this class.

This means that every Java class has Object as root in the hierarchy, not necessarily as its immediate parent.

share|improve this answer

answered Aug 31 at 9:53

fantaghirocco

3,57952436

share|improve this answer

share|improve this answer

answered Aug 31 at 9:53

fantaghirocco

3,57952436

answered Aug 31 at 9:53

fantaghirocco

3,57952436

answered Aug 31 at 9:53

fantaghirocco

3,57952436

3,57952436

add a comment | 

add a comment | 

up vote
1
down vote

No multiple inheritance means in Java a class extends only 1 class; has one immediate base class. Indirectly a class can have many ancestors: Child has Parent and Object as ancestor "super" classes.

Object --> Parent --> Child
 --> OtherChild

Relation: 1 --> N

The reason for avoiding multiple inheritance like in C++, was the ambiguity involved:

Pseudo code assuming multiple inheritance:

class A : Comparable
class B : Comparable

class Child : A, B 

 @Override A? B?
 int compareTo(Child rhs) ... super.compareTo ? ... 


A a = new Child();
B b = new Child();
a.compareTo(b);

share|improve this answer

answered Aug 31 at 9:56

Joop Eggen

73.1k65399

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  why should we care about which method to override if the signatures are identical? Overriding just implies that we are not satisfied with parents' behaviour and want to implement ours. The problem is, rather, what happens when we call child.compareTo(anotherChild) without overriding (which method are we going to invoke?)
  – Andrew Tobilko
  Aug 31 at 10:15
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AndrewTobilko well said; compareTo(a); compareTo(b), compareTo(child); actually I did not want to say anything about multiple inheritance (and interfaces) as that would be out of scope of the question. Just that multiple inheritance is not having an ancestral line; rather that single inheritance means having one (code bearing) parent per class. I also did not treat default methods in interfaces.
  – Joop Eggen
  Aug 31 at 10:30
  

  
  
  
  

add a comment | 

up vote
1
down vote

No multiple inheritance means in Java a class extends only 1 class; has one immediate base class. Indirectly a class can have many ancestors: Child has Parent and Object as ancestor "super" classes.

Object --> Parent --> Child
 --> OtherChild

Relation: 1 --> N

The reason for avoiding multiple inheritance like in C++, was the ambiguity involved:

Pseudo code assuming multiple inheritance:

class A : Comparable
class B : Comparable

class Child : A, B 

 @Override A? B?
 int compareTo(Child rhs) ... super.compareTo ? ... 


A a = new Child();
B b = new Child();
a.compareTo(b);

share|improve this answer

answered Aug 31 at 9:56

Joop Eggen

73.1k65399

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  why should we care about which method to override if the signatures are identical? Overriding just implies that we are not satisfied with parents' behaviour and want to implement ours. The problem is, rather, what happens when we call child.compareTo(anotherChild) without overriding (which method are we going to invoke?)
  – Andrew Tobilko
  Aug 31 at 10:15
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AndrewTobilko well said; compareTo(a); compareTo(b), compareTo(child); actually I did not want to say anything about multiple inheritance (and interfaces) as that would be out of scope of the question. Just that multiple inheritance is not having an ancestral line; rather that single inheritance means having one (code bearing) parent per class. I also did not treat default methods in interfaces.
  – Joop Eggen
  Aug 31 at 10:30
  

  
  
  
  

add a comment | 

up vote
1
down vote

up vote
1
down vote

No multiple inheritance means in Java a class extends only 1 class; has one immediate base class. Indirectly a class can have many ancestors: Child has Parent and Object as ancestor "super" classes.

Object --> Parent --> Child
 --> OtherChild

Relation: 1 --> N

The reason for avoiding multiple inheritance like in C++, was the ambiguity involved:

Pseudo code assuming multiple inheritance:

class A : Comparable
class B : Comparable

class Child : A, B 

 @Override A? B?
 int compareTo(Child rhs) ... super.compareTo ? ... 


A a = new Child();
B b = new Child();
a.compareTo(b);

share|improve this answer

answered Aug 31 at 9:56

Joop Eggen

73.1k65399

No multiple inheritance means in Java a class extends only 1 class; has one immediate base class. Indirectly a class can have many ancestors: Child has Parent and Object as ancestor "super" classes.

Object --> Parent --> Child
 --> OtherChild

Relation: 1 --> N

The reason for avoiding multiple inheritance like in C++, was the ambiguity involved:

Pseudo code assuming multiple inheritance:

class A : Comparable
class B : Comparable

class Child : A, B 

 @Override A? B?
 int compareTo(Child rhs) ... super.compareTo ? ... 


A a = new Child();
B b = new Child();
a.compareTo(b);

share|improve this answer

answered Aug 31 at 9:56

Joop Eggen

73.1k65399

share|improve this answer

share|improve this answer

answered Aug 31 at 9:56

Joop Eggen

73.1k65399

answered Aug 31 at 9:56

Joop Eggen

73.1k65399

answered Aug 31 at 9:56

Joop Eggen

73.1k65399

73.1k65399

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  why should we care about which method to override if the signatures are identical? Overriding just implies that we are not satisfied with parents' behaviour and want to implement ours. The problem is, rather, what happens when we call child.compareTo(anotherChild) without overriding (which method are we going to invoke?)
  – Andrew Tobilko
  Aug 31 at 10:15
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AndrewTobilko well said; compareTo(a); compareTo(b), compareTo(child); actually I did not want to say anything about multiple inheritance (and interfaces) as that would be out of scope of the question. Just that multiple inheritance is not having an ancestral line; rather that single inheritance means having one (code bearing) parent per class. I also did not treat default methods in interfaces.
  – Joop Eggen
  Aug 31 at 10:30
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  why should we care about which method to override if the signatures are identical? Overriding just implies that we are not satisfied with parents' behaviour and want to implement ours. The problem is, rather, what happens when we call child.compareTo(anotherChild) without overriding (which method are we going to invoke?)
  – Andrew Tobilko
  Aug 31 at 10:15
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  @AndrewTobilko well said; compareTo(a); compareTo(b), compareTo(child); actually I did not want to say anything about multiple inheritance (and interfaces) as that would be out of scope of the question. Just that multiple inheritance is not having an ancestral line; rather that single inheritance means having one (code bearing) parent per class. I also did not treat default methods in interfaces.
  – Joop Eggen
  Aug 31 at 10:30
  

  
  
  
  

1

1

why should we care about which method to override if the signatures are identical? Overriding just implies that we are not satisfied with parents' behaviour and want to implement ours. The problem is, rather, what happens when we call child.compareTo(anotherChild) without overriding (which method are we going to invoke?)
– Andrew Tobilko
Aug 31 at 10:15

why should we care about which method to override if the signatures are identical? Overriding just implies that we are not satisfied with parents' behaviour and want to implement ours. The problem is, rather, what happens when we call child.compareTo(anotherChild) without overriding (which method are we going to invoke?)
– Andrew Tobilko
Aug 31 at 10:15

1

1

@AndrewTobilko well said; compareTo(a); compareTo(b), compareTo(child); actually I did not want to say anything about multiple inheritance (and interfaces) as that would be out of scope of the question. Just that multiple inheritance is not having an ancestral line; rather that single inheritance means having one (code bearing) parent per class. I also did not treat default methods in interfaces.
– Joop Eggen
Aug 31 at 10:30

@AndrewTobilko well said; compareTo(a); compareTo(b), compareTo(child); actually I did not want to say anything about multiple inheritance (and interfaces) as that would be out of scope of the question. Just that multiple inheritance is not having an ancestral line; rather that single inheritance means having one (code bearing) parent per class. I also did not treat default methods in interfaces.
– Joop Eggen
Aug 31 at 10:30

add a comment | 

up vote
1
down vote

First of all, using Java 8, it is possible to accomplish Multiple inheritance using Default methods of interfaces.

Secondly, your understanding regarding Object class is correctly represented in 'Option 2'.

However, it is not multiple inheritance, rather multilevel inheritance. 'Option 1' is multiple inheritance.

Please check this link to read more about them.

share|improve this answer

answered Aug 31 at 10:07

Shashank Singh

164

add a comment | 

up vote
1
down vote

First of all, using Java 8, it is possible to accomplish Multiple inheritance using Default methods of interfaces.

Secondly, your understanding regarding Object class is correctly represented in 'Option 2'.

However, it is not multiple inheritance, rather multilevel inheritance. 'Option 1' is multiple inheritance.

Please check this link to read more about them.

share|improve this answer

answered Aug 31 at 10:07

Shashank Singh

164

add a comment | 

up vote
1
down vote

up vote
1
down vote

First of all, using Java 8, it is possible to accomplish Multiple inheritance using Default methods of interfaces.

Secondly, your understanding regarding Object class is correctly represented in 'Option 2'.

However, it is not multiple inheritance, rather multilevel inheritance. 'Option 1' is multiple inheritance.

Please check this link to read more about them.

share|improve this answer

answered Aug 31 at 10:07

Shashank Singh

164

First of all, using Java 8, it is possible to accomplish Multiple inheritance using Default methods of interfaces.

Secondly, your understanding regarding Object class is correctly represented in 'Option 2'.

However, it is not multiple inheritance, rather multilevel inheritance. 'Option 1' is multiple inheritance.

Please check this link to read more about them.

share|improve this answer

answered Aug 31 at 10:07

Shashank Singh

164

share|improve this answer

share|improve this answer

answered Aug 31 at 10:07

Shashank Singh

164

answered Aug 31 at 10:07

Shashank Singh

164

answered Aug 31 at 10:07

Shashank Singh

164

164

add a comment | 

add a comment | 

up vote
0
down vote

Option 2, as every object derives Object.class methods

share|improve this answer

answered Aug 31 at 9:43

Alexander Khlystov

12

add a comment | 

up vote
0
down vote

Option 2, as every object derives Object.class methods

share|improve this answer

answered Aug 31 at 9:43

Alexander Khlystov

12

add a comment | 

up vote
0
down vote

up vote
0
down vote

Option 2, as every object derives Object.class methods

share|improve this answer

answered Aug 31 at 9:43

Alexander Khlystov

12

Option 2, as every object derives Object.class methods

share|improve this answer

answered Aug 31 at 9:43

Alexander Khlystov

12

share|improve this answer

share|improve this answer

answered Aug 31 at 9:43

Alexander Khlystov

12

answered Aug 31 at 9:43

Alexander Khlystov

12

answered Aug 31 at 9:43

Alexander Khlystov

12

12

add a comment | 

add a comment | 

up vote
0
down vote

option 2.Object is a superclass of all other classes,but Object may not a dirrect superclass of a classe.

share|improve this answer

answered Aug 31 at 9:45

zzcron toby

63

add a comment | 

up vote
0
down vote

option 2.Object is a superclass of all other classes,but Object may not a dirrect superclass of a classe.

share|improve this answer

answered Aug 31 at 9:45

zzcron toby

63

add a comment | 

up vote
0
down vote

up vote
0
down vote

option 2.Object is a superclass of all other classes,but Object may not a dirrect superclass of a classe.

share|improve this answer

answered Aug 31 at 9:45

zzcron toby

63

option 2.Object is a superclass of all other classes,but Object may not a dirrect superclass of a classe.

share|improve this answer

answered Aug 31 at 9:45

zzcron toby

63

share|improve this answer

share|improve this answer

answered Aug 31 at 9:45

zzcron toby

63

answered Aug 31 at 9:45

zzcron toby

63

answered Aug 31 at 9:45

zzcron toby

63

63

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