How can a collection object be sorted?

by

// Sort

Collections.sort(list);

// Sort case-insensitive

Collections.sort(list, String.CASE_INSENSITIVE_ORDER);

// SortReverse-order

Collections.sort(list, Collections.reverseOrder ());

// Reverse-order sort case-insensitive

Define local, member and a class variable.

Within a method variables declared are called “local” variables.

Variables declared in the class i.e not in any methods are “member” variables (global variables).

Variables declared in the class i.e not in any methods and are called as “static” are class variables.

Name the different identifier states of a Thread.

Different types of identifiers of a Thread are:

R – Running or runnable thread

S – Suspended thread

CW – Thread waiting on a condition variable

MW – Thread waiting on a monitor lock

MS – Thread suspended waiting on a monitor lock

Define Vector class? Differentiate the Vector and ArrayList.

Vector canbe said a legacy class which has been introduced to implement the List interface since Java 2 platform v1.2

Vector is always synchronized but ArrayList is not.

When Vector class is synchronized, if we will run in multithreading environment we’ve to use ArrayList with Collections.

Vector has a default size i.e 10 while arrayList has no default size.

ArraayList is not having any method returning Enumerations where as vector list is having.

Differentiate between Enumeration and Iterator interface

In java.util package the Enumeration and Iterator are available.

The Enumeration interface is replicated by the Iterator interface.

In preference to Enumeration new implementations should consider using Iterator .

 

The difference of Iterators from enumerations are:

  • Enumeration has 2 methods namely hasMoreElements() & nextElement() where the Iterator contained three methods namely hasNext(), next(),remove().
  • An optional remove operation is added in Iterator,and has shorter method names. We Use remove() to delete the objects but the Enumeration interface does not support this feature.
  • The legacy classes use Enumeration interface .Vector.elements() & Hashtable.elements() method results Enumeration.
  • All Java Collections Framework classes returns iterator. java.util.Collection.iterator() method returning an instance of Iterator.

Collections.sort(list, String.CASE_INSENSITIVE_ORDER);

Collections.reverse(list);