Collections

• The Java Collections Framework is a collection of interfaces and classes that may be used to manipulate groups of objects.
• The classes implemented in the Java Collections Framework serve as reusable data structures and include algorithms for common tasks such as sorting or searching.
• The framework uses parameterized classes so you can use them with the classes of your choice.
• As far as manipulating collections is concerned, you may be reminded of the acronym CRUD. 


  CRUD is short for Create, Read, Update, Delete.
• The Collection interface is the highest level ofJava’s framework for collection classes and it describes the basic operations that all collection classes should implement.
• public boolean add(Base_Type new Element)

  Adds the specified element to the collection.

  Returns true if the collection is changed as a result of the call.
• public void clear ()

  Removes all of the elements from the collection.
• public boolean remove(Object o)

  Removes a single instance of the specified element from the collection if it is present.

  Returns true if the collection is changed as a result of the call.
• public boolean contains (Object o)

  Returns true if the specified element is a member of the collection.
• public boolean isEmpty ()

  Returns true if the collection is empty.
• public int size()

  Returns the number of elements in the collection.
• public Object[] to Array ()

  Returns an array containing all of the elements in the collection.

  The array is of a type Object so each element may need to be type cast back into the original base type.