Java Concepts Quiz

Where is a local variable stored in Java?

• Stack

• Heap

• PermGen

• Code Segment

Which memory area stores objects in Java?

• Stack

• Heap

• Method Area

• Registers

Which method returns the hash code of an object?

• hashValue()

• hash()

• hashCode()

• getHash()

What is the contract between equals() and hashCode()?

• If two objects are equal, they must have the same hash code

• If hash codes are same, objects are always equal

• They are unrelated

• Only equals() matters in Collections

What happens if you override equals() but not hashCode()?

• Compilation error

• Runtime error

• May break hash-based collections

• Nothing happens

What data structure does HashMap use internally?

• Array

• LinkedList

• Array + LinkedList/Tree

• TreeMap

Which method is used to compare contents of two strings?

• ==

• equals()

• compare()

• hashCode()

Which collection does not allow duplicates?

• List

• Set

• Map

• Queue

Which collection stores key-value pairs?

• List

• Set

• Map

• Queue

Which class implements List interface?

• HashSet

• HashMap

• ArrayList

• TreeMap