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COLLECTION Interview Questions And Answers
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Ques: 1 What is the Collections API?
Ans:
The Collections API is a set of classes and interfaces that support operations on collections of objects.
Ques: 2 What is the List interface?
Ans:
The List interface is bassically provides support for ordered collections of objects.
Ques: 3 What is the Vector class?
Ans:
The Vector class is bassically a provides the capability to implement a growable array of objects.
Ques: 4 What is an Iterator interface?
Ans:
The Iterator interface is bassically used to step through the elements of a Collection .
Ques: 5 Which java.util classes and interfaces support event handling?
Ans:
The EventObject class and the EventListener interface support event Handaling.
Ques: 6 What is the GregorianCalendar class?
Ans:
The GregorianCalendar is bassicallt provides support for traditional Western calendars
Ques: 7 What is the Local class?
Ans:
The Local class is bassically used to tailor program output to the conventions of a particular geographic, political, or cultural region .
Ques: 8 What is the SimpleTimeZone class?
Ans:
The SimpleTimeZone class is bassically provides support for a Gregorian calendar
Ques: 9 What is the Map interface?
Ans:
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.
Ques: 10 What is the highest-level event class of the event-delegation model?
Ans:
The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.
Ques: 11 What is the Collection interface?
Ans:
The Collection interface is bassically provides support for the implementation of a mathematical bag, An unordered collection of objects that may contain duplicates.
Ques: 12 What is the Set interface?
Ans:
The Set interface is bassically a use for method which provides methods for accessing the elements of a finite mathematical set. Sets do not allow duplicate elements.
Ques: 13 What is the typical use of Hashtable?
Ans:
Hash table is very important that time When a program wants to store a key value pair, one can use Hashtable.
Ques: 14 We trying to store an object using a key in a Hashtable. And some other object already exists in that location, then what will happen? The existing object will be overwritten? Or the new object will be stored elsewhere?
Ans:
The existing object will be overwritten and thus it will be lost.
Ques: 15 What is the difference between the size and capacity of a Vector?
Ans:
There are many diff :
> The size is the number of elements actually stored in the vector, While capacity is the maximum number of elements it can store at a given instance of time.
Ques: 16 Can a vector contain heterogenous objects?
Ans:
Yes, A Vector can contain heterogenous objects. Because a Vector stores everything in terms of Object.
Ques: 17 Can a ArrayList contain heterogenous objects?
Ans:
Yes, A ArrayList can contain heterogenous objects. Because a ArrayList stores everything in terms of Object.
Ques: 18 What is an enumeration?
Ans:
An enumeration is an interface containing methods for accessing the underlying data structure from which the enumeration is obtained. It is a construct which collection classes return when We request a collection of all the objects stored in the collection. It allows sequential access to all the elements stored in the collection.
Ques: 19 Considering the basic properties of Vector and ArrayList, where will you use Vector and where will you use ArrayList?
Ans:
The basic difference between a Vector and an ArrayList is that :
> Vector is synchronized while ArrayList is not. Thus whenever there is a possibility of multiple threads accessing the same instance, one should use Vector. While if not multiple threads are going to access the same instance then use ArrayList.
> Non synchronized data structure will give better performance than the synchronized one.
Ques: 20 What is HashMap and Map?
Ans:
Basic diff are there :
> Map is Interface and Hashmap is class that implements this interface.
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