There is however a subtle difference. The runtime library is written in the language itself, the language built-ins are written in whatever the language compiler/interpreter is written in. I have found the ability to use the debugger almost all the way down to the bare metal very useful at times. Occasionally you just need to see what some obscure internal variable is, so you can HIT that special case that will make your code work.A major reason for Java being hard to use is the enormous size of the runtime library, which just grows and grows and grows. Did you know that you can do XSLT transformation, schedule tasks to be run every night at 2 AM, and parse HTML just with the standard Java libraries? 
I laugh, and/or roll my eyes, whenever I look at the size of the runtime library for Java, C, or any other "modern small language," and/or I hear people criticizing languages like PL/I because all their built-in functionality makes them so huge.
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