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Core Java - Interview Questions and Answers for 'Object cla' - 5 question(s) found - Order By Rating

 Q1. What is the use of Object class ?Core Java
Ans. 1. Default definition for some of the methods , like equals, hashcode etc that gets carried to all objects even if you don't define anything. But that default definition is kind of like assigning 0 to integer, it just provide a safe state , nothing much for comparison.

2. Places where you have no idea about what object you may receive and just want to perform out of 8 basic methods of object class, something like printing their string representation ( defined by their toString method ), or equality ( using their equals method )

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   Like         Discuss         Correct / Improve     object class


 Q2. Can we override wait() or notify() methods?Core Java
Ans. wait and notify are declared final in object class and hence cannot be overridden.

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   Like         Discuss         Correct / Improve     object class methods  wait  notify


Very frequently asked. Among first few questions in almost all interviews. Among Top 5 frequently asked questions. Frequently asked in Indian service companies (HCL,TCS,Infosys,Capgemini etc based on multiple feedback ) and Epam Systems
  Q3. Difference between == and .equals() ?Core Java
Ans. "equals" is the method of object class which is supposed to be overridden to check object equality, whereas "==" operator evaluate to see if the object handlers on the left and right are pointing to the same object in memory.

x.equals(y) means the references x and y are holding objects that are equal. x==y means that the references x and y have same object.

Sample code:

String x = new String("str");
String y = new String("str");

System.out.println(x == y); // prints false
System.out.println(x.equals(y)); // prints true

  Sample Code for equals

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   Like         Discuss         Correct / Improve     java   string comparison   string   object class   ==    equals   object equality  operator   == vs equals   equals vs ==     Asked in 294 Companies      basic        frequent

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 Q4. Which String class does not override the equals() and hashCode() methods, inheriting them directly from class Object?Core Java
Ans. java.lang.StringBuffer.

  Sample Code for StringBuffer

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   Like         Discuss         Correct / Improve     java   object class   stringbuffer      expert        rare


Frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q5. What are the methods of Object Class ?Core Java
Ans. clone() - Creates and returns a copy of this object.

equals() - Indicates whether some other object is "equal to" this one.

finalize() - Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

getClass() - Returns the runtime class of an object.

hashCode() - Returns a hash code value for the object.

toString() - Returns a string representation of the object.

notify(), notifyAll(), and wait() - Play a part in synchronizing the activities of independently running threads in a program.

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   Like         Discuss         Correct / Improve     java   oops   object class     Asked in 16 Companies      basic        frequent

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 Q6. Which of following is not the method of object class ?Core Java
a. run
b. notify
c. wait
d. clone

Ans.a. run


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