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Difference between JIT and JVM in Java
When we start learning Java, we often come across the terms like JIT and JVM. Having a good understanding of the relationship and differences between both terms is crucial, as they are part of fundamental concepts in the Java programming language. JVM is the main component of the Java Runtime Environment that executes Java bytecode, whereas JIT is a compiler available in the JVM. This article aims to explain the difference between JIT and JVM.
JIT vs JVM in Java
JVM
It is an acronym that stands for Java Virtual Machine. The name itself suggests that it is something that does not physically exist. The JVM is a platform dependent software component of the Java Runtime Environment. However, it can execute any programs of different platforms that are compiled into Java bytecode, even those programs written in other programming languages and subsequently converted into bytecode. Here, platform means various operating systems like Mac and Windows. The Java bytecode is an intermediate representation of Java source code that is compiled by the Javac compiler.
Along with providing a platform independent and secure environment for running Java applications, the JVM also manages memory allocation, garbage collection, exception handling, threading, and other features of the Java language.
The following points conclude the tasks performed by JVM −
Loading the code.
Verification of code.
Execution of code.
Providing a secure runtime environment.
JIT
It is an acronym that stands for Just in Time Compiler. It is said as the heart of Java Virtual Machine. It enhances the performance of JVM by compiling the parts of byte code with similar functionality at the same time. This process reduces the overall time needed for the conversion of byte code to machine specific code at runtime
The JIT analyzes the bytecode to identify the hot spots, which are the sections of code that are executed more often than others. It then compiles those hot spots into native code and caches them for future use. This reduces the interpretation overhead and hence, increases the execution speed
Remember, JIT is an optional feature of the JVM and by default, it is enabled but we can enable or disable it by using command line options or system properties. Different implementations of JVM may have different JIT compilers with distinct optimization techniques
Difference between JIT and JVM
From the above discussion, we can conclude the following differences between JIT and JVM −
JIT |
JVM |
|---|---|
It is a compiler |
It is an interpreter. |
It is an optional component that may or may not be used. |
It is not an optional component. |
The JIT provides platform specific optimization. |
The JVM provides platform independence and portability for Java applications |
It is a part of JVM that enhances its performance. |
It is a part of JRE used to read and run the bytecode. |
It converts only the reusable part of byte code to machine code. |
It converts bytecode to machine code |
Conclusion
Most companies ask candidates to explain JIT vs JVM in their job interviews. But, the new Java developers often get confused between the Virtual Machine and the Just in Time Compiler. This article explained the distinction between these two concepts. Both work together to provide a fast, secure and reliable execution environment for Java applications. JVM ensures that Java programs can run on any platform without any modification on the other hand, JIT enhances the performance of JVM.
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