Tokenizing Strings

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Tokenizing Strings
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Tokenizing Strings

• Tokens are substrings separated by a delimiter
  character (string)
• StringTokenizer is used to tokenize strings
• It belongs to package java.util

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Tokenization Example

• String s "String to be broken"
• StringTokenizer st
• new StringTokenizer(s)
• String token
• while ( st.hasMoreElements() )
• token st.nextToken()
• System.out.println(token)

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Tokenization Example Output

• String
• to
• be
• broken

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Another Tokenization Example

• String s String,Separated,By,Commas"
• StringTokenizer st
• new StringTokenizer(s,,)
• String token
• while ( st.hasMoreElements() )
• token st.nextToken()
• System.out.println(token)

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Tokenization Example Output

• String
• separated
• by
• commas

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Using JOptionPane for input and output
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JOptionPane

• Resides in javax.swing package
• Used for showing different kind of dialog boxes

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Displaying Messageboxes

• Following line of code displays a simple
  messagebox
• JOptionPane.showMessageDialog( null,
• Message Title,
• Message text,
• JOptionPane.PLAIN_MESSAGE)

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JOptionPane.showMessageDialog( null, Message
Title, Message text, JOptionPane.PLAIN_ME
SSAGE)

• Argument 1 Parent Component
• Argument 2
• Argument 3

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Argument 4

• JOptionPane.PLAIN_MESSAGE

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Argument 4

• JOptionPane.QUESTION_MESSAGE

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Argument 4

• JOptionPane.WARNING_MESSAGE

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Argument 4

• JOptionPane.INFORMATION_MESSAGE

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Argument 4

• JOptionPane.ERROR_MESSAGE

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Taking Input

• String s
• s JOptionPane.showInputDialog( Enter a
  number)

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• Always returns a string
• Blocks for input
• Convert the String s to an integer by
• int i Integer.parseInt( s )

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Lets get Object Oriented

• Introduction to classes

• class Name
• Name() // Constructor

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Lets get Object Oriented

• Every class has a method named exactly same as
  the class, called Constructor
• If you dont define one, a default constructor is
  automatically created, for example for class
  named Name, default constructor looks like
• Name()

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Lets get Object Oriented

• For every class, you can have multiple
  constructors with different arguments (but
  obviously the same name)
• class Name
• Name()
• Name(String s)

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Class member functions

• class Name
• Name() // Constructor
• public void memberFunc(int x)
• // Body here

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Copy Constructor

• class Name
• int a, b, c
• Name(final Name n)
• a n.a
• b n.b
• c n.c

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Using Copy Constructor

• class Test
• public static void main(String a)
• Name n new Name()
• Name m new Name(n)

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Member functions

• All member functions along with their bodies must
  be typed inside the class code.
• There is no concept of inline functions in java
• There is no concept of prototypes either

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Method Overloading

• Member function overloading in Java is similar to
  that of C
• Declare two functions with same name but
  different arguments to make them overloaded

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Method Overloading Example

• class Name
• public myMethod()
• public myMethod(String s)

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Recursion

• Calling a function from within itself is called
  recursion
• Recursion is allowed in Java as it is in C

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Recursion Example

• class Recursive
• public int function(int i)
• if(i1 i0)
• return 1
• else
• return i function(i-1)

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Creating Packages

• package something
• class ABC
• Associates ABC in package something
• Put ABC.java file in a folder named something
• Compile normally

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Creating sub-packages

• package something.anything
• class XYZ
• Associates XYZ in package something.anything
• Put XYZ.java file in a folder named anything
  placed inside another folder something
• Compile normally

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Access Attributes in java

• Ever data member and every member function in a
  class must be assign an access attribute in java.
  
• Following are the access attributes in java
• No access attribute specified
• Public
• Private
• Protected

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Access Attribute

• No access specified
• class Test
• int x
• x is accessible from methods in any class in the
  same package

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Access Attribute

• public
• class Test
• public int x
• x is accessible from methods in any class anywhere

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Access Attribute

• private
• class Test
• private int x
• x is accessible only from methods inside the
  class. No access from outside

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Access Attribute

• protected
• class Test
• protected int x
• x is accessible from methods in any class in the
  same package and from any sub-classes anywhere