Java 1.5

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Java 1.5
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Reason for changes

• The new language features all have one thing in
  common they take some common idiom and provide
  linguistic support for it. In other words, they
  shift the responsibility for writing the
  boilerplate code from the programmer to the
  compiler. --Joshua Bloch, senior staff
  engineer, Sun Microsystems

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New features--maybe

• Generics
• Compile-time type safety for collections without
  casting
• Enhanced for loop
• Eliminates the drudgery and error-proneness of
  iterators
• Autoboxing/unboxing
• Avoids manual conversion between primitive types
  (such as int) and wrapper types (such as Integer)
• Typesafe enums
• Provides all the well-known benefits of the
  Typesafe Enum pattern
• Static import
• Lets you avoid qualifying static members with
  class names
• Metadata
• Tools to generate boilerplate code from
  annotations in the source code
• Leads to a "declarative" programming style where
  the programmer says what should be done and tools
  emit the code to do it

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Generics

• A generic is a method that is recompiled with
  different types as the need arises
• The bad news
• Instead of saying List words new ArrayList()
• You'll have to say ListltStringgt words
  new ArrayListltStringgt()
• The good news
• Provides compile-time checking to make sure you
  are using the correct type
• No casting instead of String title
  ((String) words.get(i)).toUppercase()you use
  String title words.get(i).toUppercase()

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Enhanced for loop

• Instead of void cancelAll(Collection c)
  for (Iterator i c.iterator() i.hasNext()
  ) TimerTask tt (TimerTask)
  i.next() tt.cancel()
  
• You will be able to use void
  cancelAll(Collection c) for (Object o
  c) ((TimerTask)o).cancel()
• Or void cancelAll(CollectionltTimerTaskgt c)
  for (TimerTask task c)
  task.cancel()
• Not everyone likes this syntax!

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Autoboxing

• Java wont let you use a primitive value where an
  object is required--you need a wrapper
• Similarly, you cant use an object where a
  primitive is required--you need to unwrap it
• Java 1.5 makes this automatic
• MapltString, Integergt m
  new TreeMapltString, Integergt() for
  (String word args) m.put(word,
  m.get(word) 1)

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Enumerations

• An enumeration, or enum, is simply a set of
  constants to represent various values
• Heres the old way of doing it
• public final int SPRING 0public final int
  SUMMER 1public final int FALL 2public
  final int WINTER 3
• This is a nuisance, and is error prone as well
• Heres the new way of doing it
• enum Season winter, spring, summer, fall

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Advantages of the new enum

• They provide compile-time type safety
• int enums don't provide any type safety at all
• They provide a proper name space for the
  enumerated type
• With int enums you have to prefix the constants
  to get any semblance of a name space.
• They're robust
• int enums are compiled into clients, and you have
  to recompile clients if you add, remove, or
  reorder constants.
• Printed values are informative
• If you print an int enum you just see a number.
• Because they're objects, you can put them in
  collections.
• Because they're essentially classes, you can add
  arbitrary fields and methods

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New features of enum

• public enum Coin penny(1), nickel(5),
  dime(10), quarter(25) Coin(int value)
  this.value value
• private final int value
• public int value() return value

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Static import facility

• import static org.iso.Physics.class Guacamole
  public static void main(String args)
  double molecules AVOGADROS_NUMBER
  moles ...
• You no longer have to say Physics.AVOGADROS_NUMBER

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Metadata

• Boilerplate is code that is inserted over and
  over again, into many different programs
• The _at_ symbol is used to tell the compiler to
  fetch the code from somewhere else, and insert it
• It is unclear to me how else this will be used
• I doubt that its just an insert facility

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Status

• Java 1.5 is due out in late 2003
• At this point, it seems highly unlikely that 1.5
  will be out by the end of 2003
• My description is from an ancient article--May
  2003
• It isnt easy to find out much more than this
• Lets hope for the best!

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The End