Top Most Collection class Interview Questions

·         Given,

Object a = new LinkedHashSet();

Then a instanceof HashSet is true because linkedHashSet extends HashSet.

·         We get similar results with LinkedHashMap and HashMap since LinkedHashMap extends HashMap.

·         Remember these points

Ø  Collection → interface

Ø  Collections and Arrays→ classes providing utility methods for various operations.

·         ListIterator is an interface which extends only Iterator interface not List interface

·         Enumeration interface was introduced in java 1.0

·         Iterator was added in java 1.2

·         Iterator methods : -

Ø  hasNext();

Ø  next();

Ø  remove(Object);

·         Enumeration interface has methods

Ø  hasMoreElements();

Ø  nextElement();

·         the default number of rows visible in a List is ‘4’.

·         When we add the same element again into a Set using add(Object) then the subsequent additions of the element returns a boolean false in its reurn part.