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Java Compilation Process

Last Updated on March 20, 2023 by Prepbytes

Java codes are not assembled into executable files. They are assembled into object code and then executed by the JVM at runtime (Java Virtual Machine). When we use the java compiler, we convert Java source code to bytecode. The bytecode is stored on the disc using the file extension.

Compilation Process in Java

The source code of a Java code is compiled into an intermediate binary code known as the Bytecode during the Java compilation process. The machine cannot directly execute this Bytecode. A virtual machine known as the Java Virtual Machine, or JVM, understands it. JVM includes a Java interpreter that converts Bytecode to target computer machine code. JVM is platform-specific, which means that each platform has its own JVM. However, once the proper JVM is installed on the machine, any Java Bytecode code can be run. This is shown in the diagram below:

Java application development (implementation) and can be broken down into the following phases:

A special application called a compiler, executes our Java program on what is known as a virtual Java machine (JVM).

The compiler transforms source code into so-called JVM bytecode, or machine code read by JVM. In addition, the compiler should check the code for lexical and semantic issues and optimise it.

Interpretation is the process of analyzing machine code and running it. The interpreter is a unique program that does these tasks.

The full procedure is represented in the diagram below:

Compilation vs Interpretation:
In Java, compilation and interpretation are two different processes that are used to execute Java code.

Compilation Interpretation
Compilation is the process of converting the Java source code into an executable form, known as bytecode. Interpretation is the process of executing the Java bytecode directly by the JVM.
The Java compiler takes the source code and produces bytecode, which is then executed by the Java Virtual Machine (JVM). The bytecode is loaded into the JVM, and the JVM interprets the bytecode and executes the program.
The code cannot be compiled because of compilation errors. Debugging is mainly done in run-time.
Compared to interpreted compiled programs operate faster. When an interpreted program executes, changes can be made.

The key differences between compilation and interpretation in Java are:

Compilation converts source code into bytecode, whereas interpretation executes bytecode directly by the JVM.

  • The compilation is done once during the development process, while interpretation happens each time the program is run.
  • Compilation allows for the optimization of the code, while interpretation provides greater flexibility and dynamic behavior.
  • Overall, both compilation and interpretation play important roles in Java programming, and the choice of which to use will depend on the specific needs of the program.

Compile Process:

JVM(Java Virtual Machine)

  • JVM stands for Java Virtual Machine. It is software that provides a runtime environment to execute Java code or other programming languages that target the JVM.
  • The JVM is responsible for interpreting and executing Java bytecode, which is a compiled version of the Java source code. It also provides features like memory management, security, and platform independence.
  • One of the key advantages of using the JVM is that it allows developers to write code in Java or other JVM-compatible languages and run it on any platform that has a JVM installed, without having to worry about the underlying hardware or operating system.
  • Some popular JVM languages include Java, Kotlin, Scala, and Groovy. The JVM is widely used in enterprise software development, web development, and mobile app development.

JIT( Just-In-Time ):

  • It is to transform bytecodes into native machine code at runtime, the Just-In-Time (JIT) compiler, a part of the runtime environment, improves the performance of Java applications.
  • Classes, the building blocks of Java applications, include platform-neutral bytecodes that a JVM can be a variety of computer architectures. The JVM loads the class files at runtime analyses the semantics of every individual bytecode and executes the necessary computation.
  • A Java application runs slower than a native application due to the increased CPU and memory requirements during interpretation. By converting bytecodes into native machine code at run time, the JIT compiler contributes to the performance enhancement of Java applications.
  • By default, the JIT compiler is turned on. When a method is compiled, the JVM directly invokes the method’s compiled code rather than interpreting it. The speed of the Java code could theoretically approach that of a native application if compiling every method did not require processing time and memory use.
  • JIT compilation does use memory and the processor. The JVM calls thousands of methods when it first starts up. Even if the software eventually achieves extremely good peak performance, compiling all of these techniques can greatly affect starting time.

The compilation process in Java is an important step in the software development lifecycle. It converts the human-readable source code into a platform-independent bytecode format that can be executed by the Java Virtual Machine (JVM). The Java compiler checks the syntax and semantics of the source code and generates bytecode that can be run on any platform with a compatible JVM.

Frequently Asked Questions(FAQ):

1. What is the objective of Java compilation?
Compiling a Java program entails converting the computer programmer text in your program file (also known as source code) to bytecodes, which are platform-independent guidelines for the Java Virtual Machine.

2. Is it possible to compile a Java file without the main method?
Yes, by using a static block, you can compile and execute without a main method.

3. Can we run a Java code without first compiling it?
Java 11 allows you to run Java code without having to compile it. It means that we can run Java code in a single step. Before Java 11, if we wanted to run a Java file, we had to compile it first and then run it.

4. How does compilation happen?
The compilation process involves converting source code to object code. It is accomplished with the assistance of the compiler. The compiler checks the source code for syntactical or structural errors and generates the object code if the source code is error-free.

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