The Difference Between default-jdk, ecj, gcj, and openjdk Explained

In the world of Java development, there are several different tools and packages available for developers to use. Among these are default-jdk, ecj, gcj, and openjdk. Each of these packages serves a unique purpose and offers its own set of features. In this article, we will delve deep into the differences between these four packages, providing you with a comprehensive understanding of what each one does.

Default-jdk

The default-jdk package is essentially a meta-package that depends on openjdk-7-jdk and default-jre-headless. It is designed to install the “Standard Java or Java compatible Development Kit” for the i386 architecture.

For example, to install default-jdk, you would use the following command:

sudo apt-get install default-jdk

This command installs the default Java Development Kit (JDK) on your system. The JDK is a software development environment used for developing Java applications and applets.

ECJ (Eclipse Java Compiler)

ECJ, or the Eclipse Java Compiler, is a standalone version of the Eclipse JDT (Java Development Tools) compiler, which is distributed as part of the Eclipse IDE. It is compatible with Java versions 1.3 through 1.7 and can be used to compile Java source code without installing the full Eclipse IDE.

To use the ecj compiler, you would use the following command:

ecj HelloWorld.java

In this command, HelloWorld.java is the Java source code file that you want to compile. The ecj compiler will then compile this source code into a bytecode file that can be run on the Java Virtual Machine (JVM).

GCJ (GNU Compiler for Java)

GCJ, or the GNU Compiler for Java, is a front end to the GCC (GNU Compiler Collection) that can natively compile both Java source code and bytecode files. It can also generate class files. GCJ includes other Java development tools from the classpath package and provides a Java-SDK-like interface to the GCJ toolset.

For example, to compile a Java source code file with gcj, you would use the following command:

gcj --main=HelloWorld -o hello HelloWorld.java

In this command, --main=HelloWorld specifies the name of the class that contains the main method, -o hello specifies the output file name, and HelloWorld.java is the Java source code file that you want to compile.

OpenJDK

OpenJDK is an open-source implementation of the Java SE (Standard Edition) Platform. It is a development environment for building applications, applets, and components using the Java programming language. The openjdk packages are built using the IcedTea build support and patches from the IcedTea project.

To install OpenJDK on your system, you would use the following command:

sudo apt-get install openjdk-7-jdk

This command installs the OpenJDK 7 JDK on your system. The JDK includes tools useful for developing and testing programs written in the Java programming language and running on the Java platform.

Conclusion

In conclusion, default-jdk, ecj, gcj, and openjdk each serve their own unique purposes in the world of Java development. Default-jdk is a meta-package that installs the default JDK on your system, ecj is a standalone Java compiler, gcj is a front end to the GCC that can natively compile Java source code and bytecode files, and openjdk is an open-source implementation of the Java SE Platform. By understanding the differences between these packages, you can choose the right tool for your specific needs.