The first versions of java were pretty slow.
Java performance has gotten a lot better with aggressive just-in-time-compiler (JIT) techniques.
Java performance is now similar to C -- a little slower in some cases, faster in a few cases. However memory use and startup time are both worse than C.
Java performance gets better each year as the JVM gets smarter. This works, because making the JVM smarter does not require any great change to the java language, source code, etc.

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