Java byte code is really a powerful mechanism which makes Java a portable and platform-independent programming language. There are two software components which go along and make this byte code a magical code. The two software components are compiler and interpreter. The first is the compiler which basically generates the byte code or the machine code of our Java program, and the second is the interpreter, which actually executes the byte code on the system. And this interpreter is also called JVM or Java Virtual Machine. So, in short, basically, byte code is the common piece between the compiler which creates it and the interpreter or Java Virtual Machine which actually runs it.
Let's understand more about this byte code.
Let us know why Java’s intermediary code is called byte code.
By the above information, as we know about the two software works along with byte code, we can say that byte code is a highly optimized set of instructions designed to be executed by the Java run-time system. It can also be called the intermediate representation of a Java program. It is a non-runnable code. It’s called byte code because each instruction is of one or two bytes. And the other thing is JVM is an interpreter for bytecode. So as mentioned above, the Java compiler first compiles our Java code to byte code, and then the JVM converts byte code into machine code; the Java programming language is independent because of bytecode and Java Virtual Machine. The main reason why Java is portable is that we can use Java byte code on any platform without doing any modifications that support the Java programming language. We can say that this Java byte code is portable. And we can use this Java byte code on any other major platform.
Let us know how this Java provides high performance.
The reason why Java provides high performance is Java programming language uses Just in Time (JIT). And this JIT enables high performance. And this JIT is a program. This program turns the Java byte code into machine code.
Is JVM an Overhead?
JVM is an extra layer that translates byte code into machine code.
Let's understand the difference between how the C++ compiler and Java Compiler work.
- C++ Compiler – Source Code à Machine Code
- Java Compiler – Source Code à [javac] Byte Code à JVM Byte Code à [JIT] Machine Code
If we observe the first one, we can observe that the source code in C++ is directly transformed into machine code.
And if we observe the second one, we can observe that in Java, we have the intermediate layer where we can produce the byte code and then by the Just in Time compiler. Though it looks like an overhead, this is an additional translation that allows Java to run applications on any platform. And the translation to the machine code is the underlying operating system loader.
What is This Class Loader?
When we compile a Java class, it transforms it into the form of byte code that is a platform and machine-independent compiled program and stores it as a .class file. After that, when we try to use a class, the Java class loader loads that class into memory.
Importance of Byte Code
On the principle of Write Once Deploy Anywhere (WODA), Java is built. So, there is no need to tweak a Java source code if we want to deploy it in another operating system as we know that in the end, the Java program needs a Java virtual machine to run on. And the other thing is the JVM being machine language specific, cannot be platform-neutral.
So, we have an intermediary compilation of source code - called bytecode. Bytecode is the result of compiling a .Java file and creating a .class file. Bytecode is portable and platform agnostic. If you want to run your Java program on another machine, you simply need to send the bytecodes to that machine. So, we have an intermediary compilation of source code - called bytecode. Bytecode is the result of compiling a .Java file and creating a .class file. Bytecode is portable and platform agnostic. If you want to run your Java program on another machine, you simply need to send the bytecodes to that machine.