Added to developers' whiteboard

String b = "some string";
StringBuffer sb = new StringBuffer();
sb.append("a" + b + "c");
sb.append("a").append(b).append("c");


'Nuff said.

Note to future language designers: make sure "+" is an efficient operation, maybe by having it return some sort of temporary "not concatenated yet" list of strings and resolve the catenation at the very end. This would be possible to pull off in C++ given the powerful type system and pass-by-value semantics (and it would literally rock if move constructor made it into the language!). It's not possible in Java, so we have to tell people to be careful. And for some reason, there are a some people who aren't.

Reminds me of the equivalent problem in Python:

b = 'some string'
sb = 'a'
sb += b
sb += 'c'
sb = ['a']
sb.append(b)
sb.append('c')
sb = ''.join(sb)


But notice that it's more a problem of incremental appending than one of usual concatenation. At least, 'a' + b + 'c' will not produce a temporary "string buffer" object on top of the extra temporary strings. Besides, Python does not have pretensions as being the new systems programming language...

Some would argue that neither does Java, but I disagree; witness the number of client apps being written in that language because that's what graduates are taught, and because people can't handle language where the GC does not come by default (make no mistake, the Boehm GC is available for C++ and works very well).