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Core java - Interview Questions and Answers for 'Goldman sachs' - 15 question(s) found - Order By Newest

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 )
  Q1. Difference between == and .equals() ?Core Java
Anonymous
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     Asked in 289 Companies      basic        frequent

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  Q2. What is a Lambda Expression ? What's its use ?Core Java
Admin
info@buggybread.com
Ans. Its an anonymous method without any declaration.

Lambda Expression are useful to write shorthand Code and hence saves the effort of writing lengthy Code.

It promotes Developer productivity, Better Readable and Reliable code.

  Sample Code for lambda

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   Like         Discuss         Correct / Improve     java   java8   lambda expression   architecture     Asked in 57 Companies      expert        frequent

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Basic and Very Frequently asked.
  Q3. What is Polymorphism in Java ?Core Java2016-11-06 09:10:54

Ans. Polymorphism means the condition of occurring in several different forms.

Polymorphism in Java is achieved in two manners

1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas

2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

  Sample Code for overloading

  Sample Code for overriding

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   Like         Discuss         Correct / Improve     polymorphism  object oriented programming (oops)  oops concepts  oops concepts     Asked in 107 Companies      Basic        frequent

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Frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q4. What are the methods of Object Class ?Core Java
Anonymous
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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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q5. What is a final method ?Core Java
Anonymous
Ans. Its a method which cannot be overridden. Compiler throws an error if we try to override a method which has been declared final in the parent class.

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   Like         Discuss         Correct / Improve     java   oops   final   final method     Asked in 30 Companies      basic        frequent

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Advanced level question usually asked in High end product companies. Have been asked in Google and Amazon (Based on 1 Feedback)
  Q6. Describe, in general, how java's garbage collector works ?Core Java
Anonymous
Ans. The Java runtime environment deletes objects when it determines that they are no longer being used. This process is known as garbage collection. The Java runtime environment supports a garbage collector that periodically frees the memory used by objects that are no longer needed. The Java garbage collector is a mark-sweep garbage collector that scans Java dynamic memory areas for objects, marking those that are referenced. After all possible paths to objects are investigated, those objects that are not marked (i.e. are not referenced) are known to be garbage and are collected.

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   Like         Discuss         Correct / Improve     java   garbage collection   java memory management   advanced     Asked in 21 Companies      intermediate        frequent

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q7. What is a Final Variable ?Core Java
Anonymous
Ans. Final variable is a variable constant that cannot be changed after initialization.

  Sample Code for final variable

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   Like         Discuss         Correct / Improve     oops   java   final   final variable   basic interview question     Asked in 12 Companies      basic        frequent

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 Q8. What is a ConcurrentHashMap ?Core Java
Admin
info@buggybread.com
Ans. ConcurrentHashMap is a hashMap that allows concurrent modifications from multiple threads as there can be multiple locks on the same hashmap.

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   Like         Discuss         Correct / Improve     java   collections   hashmap   map   concurrenthashmap   concurrenthashmap  concurrency   general electric   ge     Asked in 32 Companies        rare


 Q9. Difference between Abstract and Concrete Class ?Core Java
Anonymous
Ans. Abstract classes are only meant to be sub classed and not meant to be instantiated whereas concrete classes are meant to be instantiated.

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   Like         Discuss         Correct / Improve     java   oops   abstract classes   basic interview question     Asked in 1 Companies      basic        frequent


Very frequently asked. Usually asked with questions related to String.
  Q10. What is an Immutable Object ?Core Java
Anonymous
Ans. Object that can't be changed after instantiation.

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   Like         Discuss         Correct / Improve     java   oops   immutable  immutability     Asked in 27 Companies      basic        frequent

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  Q11. Why java doesn't support multiple Inheritance ?

or

Explain Java Diamond Problem.
Core Java2017-01-09 11:45:34

Ans. class A {
void test() {
System.out.println("test() method");
}
}

class B {
void test() {
System.out.println("test() method");
}
}

Suppose if Java allows multiple inheritance like this,

class C extends A, B {
}

A and B test() methods are inheriting to C class.

So which test() method C class will take? As A & B class test() methods are different , So here we would Facing Ambiguity.

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   Like         Discuss         Correct / Improve     multiple inheritance  object oriented programming (oops)  oops concepts  diamond problem     Asked in 20 Companies      basic        frequent


Frequently asked in face to face interviews.
  Q12. Write a program to print fibonacci series.Core Java

Ans. int count = 15;
int[] fibonacci = new int[count];
fibonacci[0] = 0;
fibonacci[1] = 1;
for(int x=2; x < count; x++){
fibonacci[x] = fibonacci[x-1] + fibonacci[x-2];
}

for(int x=0; x< count; x++){
System.out.print(fibonacci[x] + " ");
}

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   Like         Discuss         Correct / Improve     ebay   fibonacci series     Asked in 66 Companies      basic        frequent


 Q13. Can there be a Thread without a Process ?Core Java2016-11-30 20:50:27

Ans. No.

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   Like         Discuss         Correct / Improve     Thread  Process     Asked in 1 Companies      Basic


 Q14. A Kid can go up 1, 2 or 3 stairs in one step. Write a method that takes number of steps in a stair will print all possible ways he can take.

For example , printAllCombinations(3) should print

111
12
21
3

Similarly , printAllCombinations(4) should print

1111
121
13
211
22
31
4
Core Java2017-09-15 11:59:15

Ans. public static String findStep(int n) {
if (n == 1 || n == 0)
return 1;
else if (n == 2)
return 2;
else
return findStep(n - 3) + findStep(n - 2) + findStep(n - 1);
}

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   Like         Discuss         Correct / Improve     coding     Asked in 1 Companies


 Q15. How do you make instance of an abstract class ?Core Java2018-02-08 13:18:22

Ans. By extending it to the derived class and thereby creating instance of derived class.

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   Like         Discuss         Correct / Improve          Asked in 1 Companies




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