What is JIT compiler?

Just-In-Time(JIT) compiler: It is used to improve the performance. JIT compiles parts of the bytecode that have similar functionality at the same time, and hence reduces the amount of time needed for compilation. 

The JIT compiler helps improve the performance of Java programs by compiling bytecodes into native machine code at run time.

Just-In-Time (JIT) compiler is a feature of JVM which when enabled makes the JVM analyse the method calls in byte code and compiles them to more native and efficient code. Just-In-Time (JIT) optimizes the prioritized method calls.