What file is jar?

A jar file is an archive file built in zip format with a .jar file extension. It is usually used to aggregate a large number of Java class files, related metadata and resource files into one file in order to develop Java platform application software or libraries.

jar file introduction:

In the software field, JAR files (Java Archive, English: Java Archive) are A software package file format that is usually used to aggregate a large number of Java class files, related metadata and resource (text, images, etc.) files into one file to develop Java platform application software or libraries.

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JAR file is an archive file, built in ZIP format, with .jar as the file extension. Users can use the JDK's own jar command to create or extract JAR files. You can also use other zip compression tools, but the order of entries in the zip file header is important when compressing, because the Manifest file often needs to be placed first. File names within JAR files are Unicode text.

The JAR file format offers many advantages and features, many of which are not provided by traditional compression formats such as ZIP or RAR. They include:

Security

The contents of JAR files can be digitally signed. This way, a tool that recognizes the signature can selectively grant you software security privileges that no other file can, and it can also detect whether the code has been tampered with.

Reduce download time

If an applet is bundled into a JAR file, then the browser can download the applet's class files and related resources in one HTTP transaction instead of each A file opens a new connection.

Compression

The JAR format allows you to compress files to increase storage efficiency.

Transport Platform Extensions

The Java Extensions Framework provides a way to add functionality to the Java core platform. These extensions are packaged in JAR files (Java 3D and JavaMail are developed by Sun Developed extended example).

Package Sealing

Packages stored in JAR files can optionally be sealed to enhance version consistency and security. Sealing a package means that all classes in the package must be found in the same JAR file.

Package Versioning

A JAR file can contain data about the files it contains, such as vendor and version information.

Portability

The mechanism for handling JAR files is a standard part of the Java platform core API.

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