JNCs

1
JNCs

• Java Native Classes can be declared as local
• String userInput
• String has methods userInput.equalTo( )
• Integer myInt
• myInt.parseInt( )
• Exception e
• Exception is a class with methods and
  variables - they can be accessed as e.methodName

2
Java Native Classes

• Classes that are so useful, that Java now
  includes them with the language.
• String is a JNC (thats why its capitalized).
• Why a JNC instead of just using a type?
• Because of the methods available with the JNC.

3
String as a JNC

• methods valueOf( ), equals( ), compareTo( )
• many many more methods that can be used.
• Use like this
• String userInput // userInput now has
  methods
• if (userInput exit)
• ..
• if ( userInput.equals(exit) true )
• System.exit(0)

4
JNC Declarations

• Integer, Strings, and Double have JNC equivalents
• Integer x is the same as
• Integer x new Integer( )
• String greeting is the same as
• String greeting new String( )
• Double y is the same as
• Double y new Double( )

5
But

• x, greeting, and y now have methods they can
  draw on
• Integer x
• int z
• Double y
• double q
• q x.floatValue( ) converts x to a floating
  point
• userInput x.toString( ) converts x to a String
• y.intValue( ) truncates y to an int
• y.toString( ) creates a String from y

6
But

• x, greeting, and y now have methods they can
  draw on
• String greeting
• greeting.equals( anotherString ) yields a boolean
  result
• greeting.length( ) yields an integer that
  reflects how many characters in the string
• greeting.toLowerCase( ) and greeting.toUpperCase(
  ) convert the string for you

7
other Java Native Classes

• Math some of the methods included in this class
  are sin, cos, exp, log, max, min, random, sqrt
  and tan.
• Exception methods in this class help with
  computer errors during run time.
• ActionEvent
• Graphics

8
Change input to lowercase

• makes true, True, TrUe, TRUE, tRuE, all the same
  true
• String myString
• myString stringToConvert.toLowerCase( )

9
String JNCs methods

• String greeting Hello
• String nextGreeting
• boolean test
• int x
• test greeting.equals( hello )
• x greeting.length( )
• nextGreeting greeting.toLowerCase( )
• nextGreeting greeting.toUpperCase( )
• nextGreeting greeting.substring( 2, 4 )