Open CLASS files

  • Full name
    Java Bytecode Class Format
  • Developer
  • Popularity
Have you encountered a problem with a CLASS file? Don’t you know which program opens a file with this extension? You will find all the information you need about working with a CLASS file here. In the further part of this page we have added a list of programs that should open your CLASS file. It is enough you choose a proper application for your operating system, download and install it.

What is CLASS file?

With the file extension class, CLASS files of the Java programming language are identified. (Classes Are Programming Constructs) Source code files (file extension java) are compiled into so-called (virtual) machine-readable CLASS files and contain bytecode. This bytecode is only executable in a Java virtual machine (JVM). Since there are JVMs for many different systems, Java is considered a platform-independent programming language.

More info

Each CLASS present in a source code is compiled into a separate CLASS file, which is usually summarized in a jar file. If a JVM is installed, java files can be compiled with the javac command. Alternatively one can also use a Java IDE (integrated development environment), for example Eclipse for Java.

Since there are different versions of the JVMs (1.4, 1.5 and 1.6), it may happen that a CLASS file on certain JVMs may not work. Note that JVMs CLASS can only execute files but not generate them.

The developer of Java - Sun Microsystems - has since been bought by Oracle. A common name for the JVMs is the Java Runtime Environment (JRE).

Programs which can open a CLASS file

How to open file with CLASS extension?

In order to open a file with CLASS extension one of the following programs must be installed on user’s system. If a problem with opening CLASS file occurred, it is highly possible that none of the listed programs is present on user’s system. Even if one or more said programs are installed, there may be issues related with given programs. In order to solve a problem with CLASS files, follow the instructions below.
Install Apple Jar Launcher or other program from the list

Most often resolving problems with opening CLASS files is very simple. Just install an appropriate program that supports such files. All of the listed programs support CLASS files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of CLASS files or offer file conversion options, but may not be capable of editing such files.

Set Apple Jar Launcher as the default program for opening CLASS files

It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate CLASS files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Apple Jar Launcher applications is not on the list, select "Browse" option in order to manually locate the directory where Apple Jar Launcher has been installed.


Check the section that lists most common problems with CLASS files

Sometimes problems with opening CLASS files may not lie with the application itself, but can arise due to other causes, such as:

  • File data is corrupted
  • CLASS files has been not been completely download from the internet (only a part of the data has been downloaded)
  • Currently used user account hasn’t been granted necessary privileges to open CLASS files (should that be the case, please contact your system administrator or IT specialist)
  • CLASS file was being copied from a corrupted storage device and is incomplete or data is corrupted. (Copying files from unknown or untrusted sources should be conducted with great care as such files may contain malicious software, which can damage your system)

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