Optimizing string concatenation [JEP 280]

JEP 280 is an interesting enhancement for the Java platform. Prior to Java 9, string concatenation was translated by javac into StringBuilder : : append chains. This was a sub-optimal translation methodology often requiring StringBuilder presizing.

The enhancement changed the string concatenation bytecode sequence, generated by javac, so that it uses INVOKEDYNAMIC calls. The purpose of the enhancement was to increase optimization and to support future optimizations without the need to reformat the javac's bytecode.

The use of INVOKEDYAMIC calls to java.lang.invoke.StringConcatFactory allows us to use a methodology similar to lambda expressions instead of using StringBuilder's step-wise process. This results in more efficient processing of string concatenation.