What does a just-in-time (JIT) compiler do?

Question

What does a JIT compiler specifically do as opposed to a non-JIT compiler? Can someone give a succinct and easy to understand description?

Answer 1

JIT compiler only compiles the byte-code to equivalent native code at first execution. Upon every successive execution, the JVM merely uses the already compiled native code to optimize performance.

Without JIT compiler, the JVM interpreter translates the byte-code line-by-line to make it appear as if a native application is being executed.

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