What is JAR?
JAR is a Java file. It is a compressed file type that contains all information needed to run an application all'interno of the Java framework.
Within a JAR file you will find all the classes and directories needed to run an application, as well as its metadata, logos and text files. As you can imagine, the JAR file is a compressed file, which can be decompressed using WinRar or another popular decompressor.
What do you use it for?
Java is a very common language with many uses and as such has many associated file extensions. THE file JAR in particular they are used to run applications on any Java framework. An example of this would be the Minecraft game, which runs the latest version of Java.
The most widespread use of Java files was on phones using the Java ME or Java 2ME system. These phones they used JAR files to package all their applications.
On these phones, JAD files were used in conjunction with JAD files. In this sense JAR (along with JAD files) is the old equivalent of the APK, the file we will talk about later.
What is the APK?
In case you don't know what an APK file is, we explain it to you in detail here. Basically it is a file created for package and install applications on the android system. Like JAR, it is a compressed file and this file can be decompressed using WinRar or another popular decompressor.
When installing an application on Android via the Google Store, Google Play; This is responsible for the APK file download and installation. We can also install an APK file ourselves, which many of us do when we need an app that isn't available on Google Play or our phone does not have access to the store.
APK is not only like a little brother of JAR, but it is considered an extended language of its. It is an equivalent of JAR that is used for the same functions, only in a different environment: the Android operating system.
Finally, after downloading these types of files, we recommend that you check if the APK application is safe, as some may be fake or have some kind of malware that can harm your mobile.
How to convert from one to another?
It's hard to know exactly how to convert a JAR file to an APK and the process it will depend on the type of JAR file we want to convert.
JAR applications were created for mail with Java, and if the particular application was designed for an android, just do a simple conversion. But if it isn't, we're going to need some complications.
Easy way
If the application was created to run on an Android device, and the only thing missing is the APK format, just use one of the many online converters available. One of the most popular converters are file extensions.
Use of source code
If you are a programmer and have access to the source code of the JAR file you are working with, the simplest thing is compile the source code in an APK. If you are not a programmer, we recommend that you ask for one or learn how to do it.
Using an emulator
In most cases, this is the most convenient way. There are applications for Android that are responsible for running JAR applications without the need to convert them.
The best known is MicroEMU, which is available on GitHub at the time of writing. This allows you to run applications made for Java ME, the system used by Nokia, Motorola, Sony Erickson and similar phones in the pre-smartphone era.
Another app that does this is J2ME Loader, available on Google Play. It runs applications built for Java 2ME, the original version of Java ME, also used by Nokia and its competitors a few years ago.
The most important thing in all of these processes is to take into consideration the technology you are managing. As technology advances, many very common programs and languages are forgotten. Trying to recover them can be difficult, but it's always worth it. Do not give up!