Joseph D. Darcy's Sun Weblog

Friday August 28, 2009

Project Coin: The Final Five (Or So)

First, thanks to all those who submitted interesting proposals and thoughtful comments to Project Coin; a demonstrably vibrant community wants to evolve the Java programming language!

Without further ado, the final Project Coin changes accepted for inclusion in JDK 7 are:

• Strings in switch

• Automatic Resource Management

• Improved Type Inference for Generic Instance Creation (diamond)

• Simplified Varargs Method Invocation

• An omnibus proposal for better integral literals

• Language support for Collections

• Language support for JSR 292

The specification, implementation, and testing of these changes are not final and will continue to evolve as interactions are explored and issues cleared. Two of the listed items are combinations of multiple submitted proposals. The omnibus proposal for improved integer literals includes at least binary literals and underscores in numbers; a way to better handle unsigned literals is desired too. Language support for Collections covers collection literals and allows for developing indexing access for Lists and Maps, assuming the technical problems are resolved.

That leaves a few proposals that went through further consideration, but were not accepted on the final list:

• Improved Exception Handling for Java

• Elvis and Other Null-Safe Operators

• Large arrays

Improved exception handling would be a fine change for the language, but it ventures near the type system and we do not estimate we have resources to fully develop the feature within JDK 7. I would like to see improved exception handling reconsidered in subsequent efforts to evolve the language. While the Elvis operator and related operators are helpful in Groovy, differences between Groovy and Java, such as the presence of primitive types and interactions with boxing/unboxing render the operators less useful in Java. JDK 7 will support other ways to ease the pain of null-handling, such as the null checking enabled by JSR 308. Aggregates natively supporting more than 32-bits worth of entries will no doubt be increasingly needed over time. Language support for collections may allow such facilities to be developed as libraries until the platform directly handles large data structures.

The coin-dev list will remain available for the continued refinement of the accepted changes. Further discussion of proposals not selected is off-topic for the list.

The majority of the implementation of the Project Coin changes should be in JDK 7's development Mercurial repositories by the end of October 2009.

In due course, we intend to file a JSR covering the Project Coin changes.