Java Collections

-Contains no duplicate elements.

-Can contain at most one Null value.

-Elements are not key-value pairs.

-Accessing an element can be almost as fast as performing a similar operation on an array.

Which of these classes provides the specified features?

• LinkedList

• TreeMap

• HashSet

• LinkedHashMap

• HashMap

Which of the following statement about Set is true?

• A HashSet cannot have a null value.

• Set allows duplicate values.

• Set allows null values but only single occurrence.

• Set extends the Java.util.collection interface.

-Entries are not organized as key/value pairs.

-Duplicate entries are rejected.

Which interface of the java.util package offers the specified behavior?

• List

• Map

• Set

• None of the above

List listNames = new ArrayList();

listNames.add("Tom");

listNames.add("Mary");

listNames.add("Peter");

String name2 = (String) listNames.get(1);

System.out.println(name2);

What is the output of the above code

• Tom

• Mary

• Peter

• raises Exception

What is Collection in Java?

• A group of objects

• A group of classes

• A group of interfaces

• None of the mentioned

Which of these interface is not part of Java’s collection framework?

• List

• Sorted List

• Set

• Sorted Map

Which of these interface declares core method that all collections will have?

• Collection

• EventListner

• Comparator

• Set

• List

Which interface does java.util.Hashtable implement?

• Java.util.Map

• Java.util.List

• Java.util.HashTable

• Java.util.Collection

Which collection class allows you to grow or shrink its size and provides indexed access to its elements, but whose methods are not synchronized?

• java.util.HashSet

• java.util.LinkedHashSet

• java.util.List

• java.util.ArrayList

Which of these is synchronized?

• TreeMap

• HashMap

• Hashtable

• All of the above