MIDlet

A midlet is a Java ME application designed to run on mobile devices that implement the Mobile Information Device Profile (MIDP). Midlets are packaged as Java ARchive (JAR) files and are typically distributed with a Java Application Descriptor (JAD) file that provides metadata and startup information.

Midlets run in a sandboxed environment on a Java Virtual Machine implementing CLDC (Connected Limited Device Configuration). They follow a lifecycle defined by three methods: startApp, pauseApp, and destroyApp; the system can pause or terminate a midlet, and the midlet may call notifyDestroyed to indicate it has finished.

Most midlets use the javax.microedition.lcdui package for user interfaces and storage. The available APIs are a subset of Java ME designed for small devices, with limited threading, graphics, and networking compared to standard Java.

Packaging and deployment are defined by manifest entries such as MIDlet-Name, MIDlet-Version, MIDlet-Vendor, and MIDlet-1, which specify metadata and the main class to launch. The JAD file can reference the JAR and provide constraints like required components, access permissions, and expiration.

Security for midlets is sandboxed, with permissions controlling access to resources such as the network, file system, and system properties. Some devices support digital signing to elevate privileges or enable trusted operations.

History and current status: midlets were central to Java ME on feature phones in the late 1990s and 2000s, but their usage declined with the rise of smartphones and modern app ecosystems. They persist in legacy devices and certain embedded environments, while many platforms have phased out MIDP-era support.