Java Magazine - March/April 2012

//java architect /
Project Coin: The Java Language
Has Evolved!
JULIEN PONGE
Java SE 7 offers several features for writing more-concise and safer code while not breaking backward
compatibility with existing Java code.

JAVA IN ACTION

Project Coin is an OpenJDK project that initiated the Java language changes that were standardized as part of Java SE 7 under JSR 334 in the Java Community Process (JCP). The project is self-described as follows:

“The goal of Project Coin is to determine what set of small language changes should be added to JDK 7. That list is:

■ ■ Strings in switch

■ ■ Binary integral literals and underscores in numeric literals

■ ■ Multi-catch and more precise rethrow

■ ■ Improved type inference for generic instance creation (diamond)

■ ■ try-with-resources statement

■ ■ Simplified varargs method invocation”

This article is the second part
of a series of two articles cover-
ing each item of Project Coin. The
goal is to present the immediate
usage of each feature, and also
to provide some background on
the implications in implementing
each of them, especially because
they all maintain backward
compatibility with prior versions
of Java SE. The impact of each
change was remarkably balanced
with a scientifically sound analy-
sis of millions of lines of existing
Java code.

cially useful when dealing with collections, because the generic type declaration clearly documents its intended usage and removes unnecessary casts.

The implementation strategy
for generics is a compromise
between a complete type system
and the need for backward com-
patibility with existing code bases
at the time generics were intro-
duced. To accomplish that, the
compiler knows the parameter-
ized types and performs checks
based on them, but such infor-
mation is lost at runtime. This is
called type erasure.

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Simplified varargs Method Invocation Java SE 5 introduced generics. They have since been widely adopted because of the increased safety that the compile-time type checking offers. They are espe-