Updated November 16, 2023

Introduction to Java Compilers

Java Compilers are for the programming language. Every programming language has its program that executes the code return—converting the code written in human-understandable to translate into the language understood by machines. Java is easy to understand. If we write programs in Java, they should be converted into machine language.

Machine language is nothing but 0’s and 1’s. To convert this code into byte code, java has its own set of compilers. Generally, we knew only a few compilers. And if you are new to Java, then the possibility is you must know only one compiler called Javac. Compilers give us the ability to interact with other platforms. We can run our program written in Java on any platform like Windows, Linux, MAC, etc. There is no restriction on which compiler should be used. But we should know the availability of different compilers for the time being. Now, let’s look at what exactly it means.

Introduction
What are Java Compilers?
Working
Types of Java Compilers

What are Java Compilers?

Compilers are an interface between human language and machine-understandable language. The Java compiler operates on the .java file and converts every class in the .java file into its corresponding .class file. This .class file can operate on any Operating System.

Hence, java is a platform-independent language. Compiler Javac converts our Java file into machine language. Bytecode is called bytecode. It’s time to check out different environments.

Working

Today, several Java compilers are being used in the programming industry. There are many online IDEs or interfaces where Java code can run smoothly to execute numerous codes. Some of them offer significant advantages over desktop options. Some of the points of these are given below:

Easy to set up – There are no downloads and no installation procedure.
Quickstart – Eclipse takes one minute to open otherwise
Easy sharing – Sharing between teachers and students, that is, their assignments.

Types of Java Compilers

Let us study in detail the different types of Compilers, which are as follows:

1. Java Compiler (javac)

Martin Odersky implemented it at Sun Microsystems, which Oracle further owned. This Javac compiler must be installed with any IDE to run a Java program. Javac itself is written in Java language.
The javac command is the standard Java compiler provided by Oracle (and other Java distributions).
It translates Java source code (.java files) into bytecode (.class files).
It is a command-line tool and is part of the Java Development Kit (JDK).

javac YourClass.java

2. Just-In-Time Compiler (JIT)

The Java Virtual Machine includes a Just-In-Time compiler.
The JIT compiler translates bytecode into native machine code at runtime, just before executing it, instead of compiling the entire Java program ahead of time.
This allows the JVM to adapt to the host machine’s architecture, potentially improving performance.
It improves Java application performance and is enabled by default. It becomes active when any method in Java is called.
JIT compiles the byte code of that method into machine code. It’s a component of the Java Runtime Environment that improves performance at run time.

3. Ahead-of-Time (AOT) Compiler

In addition to the traditional JIT compilation, there are efforts to introduce Ahead-of-Time compilation for Java programs.
AOT compilers generate native machine code ahead of execution, allowing Java programs to run without the need for an intermediate bytecode interpretation step.
GraalVM is an example of a Java Virtual Machine that supports AOT compilation.

4. Java Native Interface (JNI) Compiler

The Java Native Interface enables Java code to invoke and interact with applications and libraries written in other languages (e.g., C, C++).
The javah tool generates C header files from Java classes, and then developers use a C compiler to compile the native code.

javah YourClass

5. Dynamic Language Compiler (JSR 292 – InvokeDynamic)

Introduced in Java 7, the “invokedynamic” bytecode instruction allows for more flexible and efficient execution of dynamic languages on the Java Virtual Machine.
This is especially useful for languages like Groovy, Scala, and others that don’t have a static type system.

6. GCJ

GCJ stands for GNU Compiler for Java. This is a free compiler available for Java Programming Language.
This compiler compiles the Java source code to a machine-understandable format.
It can also compile JARs that contain bytecode.
This compiler is only available for UNIX and not for other Operating Systems like Windows, and it is neither available for any IDE.
This compiler can also compile C, C++, Fortran, Pascal, and other programming languages.

7. ECJ

This is an Eclipse compiler for Java, comes with Eclipse IDE, and is available for operating systems like Windows, UNIX, etc.
If there is a compile-time error in a part of the code, you can test the other part to determine whether it works fine using this compiler.
This is not the case with javac, as you need to fix all the errors before compilation.
If your Java source code has any compile-time error with the Eclipse compiler, it will go through it as a runtime exception. Also, this compiler can run in the background of IDE, and it speeds up the compilation compared to javac.

8. Jikes

Dave Shields and Philippe Charles developed this compiler at IBM, an OSI-certified open-source Java Compiler written in C++.
The high-performance compiler is suitable for large projects and compiles small projects much faster than Sun’s compiler.
Jikes was released in 1998 for Linux. The issue with the Jikes compiler is that it does not support Java 5 and above versions since there is no update from IBM.
This compiler works best with JDK 1.3 and the below versions.

9. Codiva

Developers extensively use Codiva.io as the best compiler for Java in coding and programming within the Java language interface.
The best advantage of Codiva is that it compiles the code instantly as the user types it, processes the compilation errors, and shows it in the editor. After finishing the typing, we see the compilation results shown in the respective compiler’s editor.
There is also a good provision for completion automatically. These two features save a lot of time while processing a simple or complex piece of code in the compiler.
Codiva has a feature that enables more than one file and packages. It can also have file names whose names can be given customized.
Codiva also works very smoothly on mobile platforms. Some of the disadvantages of Codiva are it supports only Java, C, or C++. Codiva supports Java 9 but doesn’t support Java 9 modules, and none of the other online compilers supports Java modules either. So, it is quite natural that it does not support Java 9 modules.

10. Jdoodle

Many programmers extensively use JDoodle, an online compiler, to run Java code on the Java platform. It supports almost 70 languages. JDoodle allows only a single file, but you don’t have to specify any filename. These are found by searching the file names.
It has excellent terminal support for running programs that interact one-to-one with the live code. The programs are run with 10-second timing.
Android Studio uses Java for building Android programs, and developers commonly employ Jdoodle as one of the compilers in this process.
It would be a great choice if one knows a lot of languages and knows how to switch between languages.
There are disadvantages to JDoodle. One disadvantage is that the code compiles after the writer or drafter has written it. The user has to find the error message, then go to the line where the error occurred and make necessary changes. People who have used Codiva before would find it very difficult to handle JDoodle in the first place. Secondly, the disadvantage of JDoodle is that it just supports one file. In the system of encapsulation, packages cannot be taught. JDoodle has many disadvantages. Despite the drawbacks, JDoodle is popular because of its numerous uses.

11. Rextester

Rextester started as a Regular Expression Tester. It grew up to be an online interface later. It’s very popular among C# users and can be used for over 30 programming languages, including Java.
In Rextester, there is variation between multiple editor widgets.
It offers excellent live collaboration support for the Java programming language. Users can easily share the URL and initiate typing with no glitches observed thus far. Multiple users can edit simultaneously.
The Rextester platform extensively uses NetBeans as its development environment.
It supports only a single file, and the class name of the file should be Rextester to get supported. Also, the class should NOT be made public.

Developers commonly use the standard Java compiler (javac) and the Just-In-Time compiler at various stages in the Java development and execution process. Developers use them frequently in day-to-day Java development.

Conclusion

Java is an Object-Oriented Programming Language that compiles the code into byte code and then runs the code on any computer system that supports Java Virtual Machine. The compiler is a program that processes the high level of the source code of a programming language written by the developer into a machine-understandable format. Programmers write these compilers in programming languages such as Pascal, C, Basic, Java, etc. In general, compilers can be written in any language which is powerful enough to write compilers.

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Introduction to Java Compilers

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