J2ME

J2ME, or Java 2 Platform, Micro Edition, is a collection of Java technologies designed for developing and running applications on mobile devices and other resource-constrained embedded systems. It provides a subset of the full Java platform, tailored for devices with limited memory, processing power, and battery life.

The core components of J2ME include the Connected Limited Device Configuration (CLDC) and the Connected Device Configuration (CDC). CLDC targets devices with minimal resources, such as feature phones, while CDC is for more capable devices like smartphones and PDAs. J2ME also defines profiles, which are sets of APIs that provide device-specific functionality. The most common profile is the Mobile Information Device Profile (MIDP), which enables the development of applications, known as MIDlets, that can run on a wide range of mobile phones.

J2ME applications are typically written in Java and then compiled into Java bytecode. This bytecode is then executed on a Java Virtual Machine (JVM) specifically designed for the target device. This approach allows for "write once, run anywhere" functionality, meaning a J2ME application could theoretically run on any device that supports the same J2ME configuration and profile.

While J2ME was once a dominant platform for mobile application development, its popularity has waned with the rise of smartphones running more advanced operating systems like Android and iOS. However, J2ME still finds use in certain embedded systems and for developing applications on older or less powerful mobile devices.