In the earlier version of Java, Compilation phase is very fast and implementation phase is very slow. This is one of the complaint received by SUN Microsystem from the Industry experts.
To speed up the Interpretation phase, SUN Microsystem has developed a program called JIT ( Just in Time compiler and added as a part of JVM)
In the current versions of the JAVA, Interpretation phase is so faster than compilation phase. Hence, SUN Micro system has populated Java is one of the Highly interpreted programming language compared to all the programming languages available in the Realworld.
JIT is the program developed by SUN micro system and added as a part of the JVM to speedup the Interpretation phase by reading the entire section of the bytecode and converting into native understanding form of OS.