Group 4: Song Li, Ying Lu,

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Java ParTy Java With Parameterized Types
Tonight Im gonna ParTy like its 1999. Prince

CS655 Programming Languages University of
Virginia Computer Science

• Group 4 Song Li, Ying Lu,
• Hexin Wang, and Michael Walker
• May 1, 2000

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Outline

• Motivation
• Related Work
• Our Solution ParTy
• Evaluation
• Remaining Work
• Conclusion

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Motivation

• Java provides no support for genericity JLS
• Must use Object parameters with type casting
• Performance hit
• Type safety is an issue

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Genericity Potential Benefits

• Ideal scenario
• One generic abstraction that adapts
• Compiled code is JVM-compatible
• Type safety control is just as powerful as
  non-generic code
• Performance boost in execution speed
• Small code size

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Genericity Potential Benefits

• ParTy scenario
• One generic abstraction that adapts
• Compiled code is JVM-compatible
• Type safety control is just as powerful as
  non-generic code
• Performance boost in execution speed
• Small code size

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Related Work

• Examine support for type parameters in other
  languages
• C, Ada, Sather, Eiffel, Haskell, ML
• Examine current proposals for Java extensions
• GJ, PolyJ, Pizza, Agesen et. al.

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Related Work GJ and Pizza Bracha98

• GJ translates into legal JVM bytecode
• Homogeneous genericity
• Substitutes type variables by their bounding
  type
• usually, Object
• Constrains code size
• Sacrifices speed
• No type constraints

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Related Work PolyJ Liskov97

• Modifies JVM bytecode to express parameterization
• better performance
• small code size
• Adds where clause type constraints a la CLU
  LSA77
• Creates a new language

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Related Work Agesen et. al. (Stanford, 1997)

• Insert preprocess step into JVM loader
• no change to JVM
• delays code blowup until load-time!
• No type constraints
• Details of implementation are vague

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Related Work Comparison
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Java ParTy Philosophy

• Provide a powerful, safe, and efficient construct
  for designing generic classes without changing
  JVM bytecodes
• Rule Do not add complexity to Java unless its
  usefulness outweighs its complexity

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Our Solution Java ParTy

• Constructed JLS-extended syntax and semantics
• Brief list of features
• type parameters within class or interface
• where clause type constraints
• type parameter can itself be of a parameterized
  type

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ParTy Code Example
class myClassltType1, Type2gt where boolean lt(
Type1 t) extends myBaseClass implements
myInterface // class body
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ParTy Implementation
ParTy class A
class AltTgt // body
(1) Generic class A written (2) class B written
to instantiate A with actual types
ParTy class B
Class B Altintgt a AltStringgt b
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ParTy Implementation
ParTy class A
(3) Classes are sent to compiler (4)
Corresponding .pclass created
ParTy compiler
class AltTgt // body
A.pclass file
ParTy class B
Class B Altintgt a AltStringgt b
B.pclass file
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ParTy Implementation
ParTy class A
(5) Regular .class files generated at load-time
ParTy compiler
ParTy preprocessor
class AltTgt // body
A_int .class
A.pclass file
A_String .class
ParTy class B
Class B Altintgt a AltStringgt b
B.pclass file
B.class
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ParTy Implementation
(6) JVM-compatible classes are run
ParTy class A
ParTy compiler
ParTy preprocessor
class AltTgt // body
A_int .class
JVM
A.pclass file
A_String .class
ParTy class B
Class B Altintgt a AltStringgt b
B.pclass file
B.class
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Qualitative Evaluation

• How useful is ParTy?
• Constructed Pair, Set, LinkedList, OrderedSet
  generic classes
• What restrictions are there?
• No where clause for individual methods
• no implicit type information allowed
• no value parameters within ltgt

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Quantitative Evaluation

• Code size
• blowup delay is good for network transmissions
• Benchmarking
• Ran ParTy code against equivalent Java
• Results...

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Quantitative Evaluation Results

• ParTy yielded code up to 27.6 faster!

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Remaining Work

• Finish ParTy compiler
• add type checks
• Support for primitive types
• Integration of ParTy preprocessor into JVM
  ClassLoader
• more extensive benchmarking

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Conclusion
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Conclusion

• ParTy provides a powerful, safe, and efficient
  construct for designing generic classes without
  changing JVM bytecodes
• ParTy code size expansion delayed until load time
• ParTy adds only the most useful features of type
  parameterization to Java