Binary Decision Tree

1
Binary Decision Tree

• Computer Science and Engineering

2
Introduction

• Binary Search Tree Key value at the root
  partitions the set of data represented in the
  tree into three disjoint sets
• A set with key value at the root
• A set of keys in the left subtree lt key value of
  the root
• A set of keys in the right subtree gt key value of
  the root
• We considered only numerical values, gt and lt
  operators.
• In a decision tree the criteria for partition is
  stored in the internal node and the data in the
  leaf nodes. When the partition is two-way we get
  a binary decision tree.
• Example
• Tree for the popular animal guessing game
• The criteria mammal could split the zoo animals
  into two sets, such other criteria could split
  the two sets further, until the splitting process
  results in a single animal kind.

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(Zoo) Animal Tree
Is it a mammal?
no
yes
no
yes
yes
no
Frog
Parrot
Does it have a long neck?
Cow
yes
no
Questions with yes or no answers at the
internal nodes Answers at the leaf nodes.
Giraffe
Tiger
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Simple Guesser no load/save
5
Builder/Guesser with save/no load
AnimalDBBuilder
BTreeInterface
java.io.Serializable
ObjectOutputStream
Visitor
BTree
OutputFile
PlayVisitor
LearnVisitor
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Guesser with simple load/save
GuesserSimpleLoadSave
BTreeInterface
java.io.Serializable
ObjectOutputStream
ObjectInputStream
Visitor
BTree
OutputFile
InputFile
PlayVisitor
LearnVisitor
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Guesser with Load/Save Visitors
GuesserLoadSave
BTreeInterface
java.io.Serializable
ObjectOutputStream
ObjectInputStream
Visitor
BTree
OutputFile
InputFile
PlayVisitor
LearnVisitor
LoadVisitor
SaveVisitor
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Load/Save (using Object Streaming)

• The capability to store and retrieve Java objects
  is essential to building persistence and
  streaming into application.
• Writing to an Object Stream
• Reading from an Object Stream
• Exception Handling
• Example See the code in the BTree example

9
Persistence

• The values of the data structures in a program
  are lost when the program terminates.
• If you want the data to exist after program
  termination you need to store it in a file or in
  a database.
• This capability of data is known as persistence.

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How to use Serialization?

• 1. import java.io.
• 2. Specify the class whose instances need to be
  stored/loaded as implementing java.io.Serializable
  interface.
• 3. Use writeObject and readObject methods whose
  header are as given below
• void writeObject (Object obj) throws
  IOException
• Object readObject() throws ClassNotFoundExcepti
  on, IOException

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Writing to an Object Stream

• // serialize various objects into a file
• FileOutputStream f new FileOutputStream(tmp)
• ObjectOutputStream s new ObjectOutputStream(f)
• s.writeObject(Today)
• s.writeObject(new Date())
• BTree t new BTree(MyName, null, null)
• s.writeObject(t)

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Reading from an Object Stream

• // Deserialize a objects from a file
• FileInputStream inf new FileInputStream(tmp)
• ObjectInputStream s1 new ObjectInputStream(inf)
  
• //read the Object and cast to retrieve the
• // actual object
• String (String)s1.readObject()
• Data date (Date)s1.readObject()
• BTree animalDB (BTree)s1.readObject()