Imported From: https://issues.scala-lang.org/browse/SI-9315?orig=1
Reporter: @retronym

@retronym said:
Also, add an overload to scala.collection.mutable.StringBuilder to accept a CharSequence.

@dragos said:
@retronym I vaguely remember the time, but I am not 100% sure. I think someone wrote scala.StringBuilder in an attempt to have less dependencies on the JVM (and share more code with the .net backend). But I might be wrong. I think there were some concerns over how good or bad this implementation was, but in the end it seemed “safe”. I agree we should just go back to java.lang

@ijuma said:
Relevant email thread:

"However, it turns out there is an very important but underdocumented jvm optimization, OptimizeStringConcat, which is enabled by default. This optimization, which is pretty much only documented by its source code (http://hg.openjdk.java.net/jdk8/jdk8/hotspot/file/87ee5ee27509/src/share/vm/opto/stringopts.cpp), is capable of turning something of approximately the form new StringBuilder().append(x).append(y)....append(z).toString() (aka about what javac would generate if you use x + y + ... + z) into a single char[] allocation of the optimal length, which is a big performance boost over what the normal java code does (2 char[] allocations at the absolute minimum if the initial size is correct, normally more)
The issue is that this same optimization doesn't work for the identical scala code."

https://groups.google.com/d/msg/scala-language/AN2Ymk1J1ik/Tpq9vpQCIQAJ

@soc said:
scala/scala#4737

@ijuma said:
Nice work. JEP 280: Indify String Concatenation is implemented in Java 9 and is related:

http://openjdk.java.net/jeps/280