1 / 12

Processing Data in Collections

Chapter 13. Processing Data in Collections. Object Wrappers. Collections can only hold objects. Primitive types ( int , double , float, etc.) are not objects. Primitives must be wrapped in special wrapper objects. Wrappers exist for each of the eight primitive types. What is an iterator?.

shelby
Download Presentation

Processing Data in Collections

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 13 Processing Data in Collections

  2. Object Wrappers • Collections can only hold objects. • Primitive types (int, double, float,etc.) are not objects. • Primitives must be wrapped in special wrapper objects. • Wrappers exist for each of the eight primitive types.

  3. What is an iterator? • An iterator is an object that encapsulates the ability to iterate through or visit each element in the collection.

  4. Using the Iterator Interface • hasNext() method determines if there are more elements in the array • next() method returns the next element and advances the iterator

  5. The DrawShapes Application • User clicks in applet window to create one of three random shapes. • Each shape is added to a collection. • When user clicks in applet window, the collection is checked to see if a “hit” is registered on an existing shape. • When a “hit” occurs, the shape’s color will change randomly.

  6. The Shape Inheritance Hierarchy • Abstract class OurShape implements: • changeColorRandomly() to change the color of an object by randomly selecting a color • contains() to determine whether x, y coordinates of a mouse click fall within a shape’s boundaries • draw() to draw the shape at x, y coordinates specified by a mouse click

  7. Classes Derived from OurShape • OurRectangle • OurTriangle • OurCircle

  8. What is a linked list? • A LinkedList is a more powerful data structure that allows for quick and easy insertion and removal of elements.

  9. Linked Lists • LinkedLists come in two types: • Singly linked list—each node knows only the next node • Doubly linked list—each node knows both the previous and the next node

  10. What is a set? • A set is a collection with no duplicate elements. • Programmer needs to determine what constitutes a “duplicate.” • The equals() method can be used to provide an additional definition of equality.

  11. HashSet • Based on a hash table, a HashSet is a powerful data structure that can be used to retrieve objects quickly in a set. • Unordered collection • A hash code is used to organize objects in a HashSet

  12. TreeSet • TreeSet provides the properties of a set in a sorted collection. • Objects can be inserted in any order but are retrieved in sorted order • Uses Comparable interface to compare objects for sorting • Primitive types and String objects are comparable • Up to programmer to implement the compareTo() method for user-defined objects

More Related