.J File Extension

Contains program source code written in the Java programming language; may include the source code for a complete program or may be one of many files referenced by a Java programming project.

Java source files most often have a .JAVA extension.

Compressed graphic that uses .JPEG image compression; may contain thousands of colors, which makes it a good format for storing digital photos; can use different levels of compression, but the more compression is used, the lower the quality of the resulting image.

Most JPEG files have a .JPG extension.

Compressed file archive created with JAR, the successor to the ARJ file compression program (which created .ARJ files); JAR is available in a 16-bit DOS version and a 32-bit Windows version.

Not related to the .JAR format, which is a Java Archive.