Java Platform, Micro Edition or Java ME is a computing platform for development and deployment of portable code for embedded and mobile devices (micro-controllers, sensors, gateways, mobile phones, personal digital assistants, TV set-top boxes, printers).  Java ME was formerly known as Java 2 Platform, Micro Edition or J2ME.
The platform uses the object-oriented Java programming language. It is part of the Java software-platform family. Java ME was designed by Sun Microsystems, acquired by Oracle Corporation in 2010; the platform replaced a similar technology, PersonalJava. Originally developed under the Java Community Process as JSR 68, the different flavors of Java ME have evolved in separate JSRs. Oracle provides a reference implementation of the specification, but has tended not to provide free binary implementations of its Java ME runtime environment for mobile devices, rather relying on third parties to provide their own.
As of 2008, all Java ME platforms are currently restricted to JRE 1.3 features and use that version of the class file format (internally known as version 47.0). Should Oracle ever declare a new round of Java ME configuration versions that support the later class file formats and language features, such as those corresponding to JRE 1.5 or 1.6 (notably, generics), it will entail extra work on the part of all platform vendors to update their JREs.
Java ME devices implement a profile. The most common of these are the Mobile Information Device Profile aimed at mobile devices, such as cell phones, and the Personal Profile aimed at consumer products and embedded devices like set-top boxes and PDAs. Profiles are subsets of configurations, of which there are currently two: the Connected Limited Device Configuration (CLDC) and the Connected Device Configuration (CDC). 
There are more than 2.1 billion Java ME enabled mobile phones and PDAs.  It is popular in sub $200 devices such as Nokia's Series 40. It was also used on the Bada operating system and on Symbian OS along with native software. Users of Windows CE, Windows Mobile, Maemo, MeeGo and Android can download Java ME for their respective environments.  
Connected Limited Device Configuration
The Connected Limited Device Configuration (CLDC) contains a strict subset of the Java-class libraries, and is the minimum amount needed for a Java virtual machine to operate. CLDC is basically used for classifying myriad devices into a fixed configuration.
A configuration provides the most basic set of libraries and virtual-machine features that must be present in each implementation of a J2ME environment. When coupled with one or more profiles, the Connected Limited Device Configuration gives developers a solid Java platform for creating applications for consumer and embedded devices. The configuration is designed for devices with 160KB to 512KB total memory, which has a minimum of 160KB of ROM and 32KB of RAM available for the Java platform.
Mobile Information Device Profile
Designed for mobile phones, the Mobile Information Device Profile includes a GUI, and a data storage API, and MIDP 2.0 includes a basic 2D gaming API. Applications written for this profile are called MIDlets. Almost all new cell phones come with a MIDP implementation, and it is now the de facto standard for downloadable cell phone games. However, many cellphones can run only those MIDlets that have been approved by the carrier, especially in North America.
JSR 271: Mobile Information Device Profile 3 (Final release on 09 Dec, 2009) specified the 3rd generation Mobile Information Device Profile (MIDP3), expanding upon the functionality in all areas as well as improving interoperability across devices. A key design goal of MIDP3 is backward compatibility with MIDP2 content.
Information Module Profile
The Information Module Profile (IMP) is a profile for embedded, "headless" devices such as vending machines, industrial embedded applications, security systems, and similar devices with either simple or no display and with some limited network connectivity.
Originally introduced by Siemens Mobile and Nokia as JSR -195, IMP 1.0 is a strict subset of MIDP 1.0 except that it doesn't include user interface APIs — in other words, it doesn't include support for the Java package
javax.microedition.lcdui . JSR-228, also known as IMP-NG, is IMP's next generation that is based on MIDP 2.0, leveraging MIDP 2.0's new security and networking types and APIs, and other APIs such as
platformRequest() , but again it doesn't include UI APIs, nor the game API.
Connected Device Configuration
The Foundation Profile is a Java ME Connected Device Configuration (CDC) profile. This profile is intended to be used by devices requiring a complete implementation of the Java virtual machine up to and including the entire Java Platform, Standard Edition API. Typical implementations will use some subset of that API set depending on the additional profiles supported. This specification was developed under the Java Community Process.
Personal Basis Profile
In contrast to the numerous binary implementations of the Java Platform built by Sun for servers and workstations, Sun does not provide any binaries for the platforms of Java ME targets with the exception of an MIDP 1.0 JRE (JVM) for Palm OS.  Sun provides no J2ME JRE for the Microsoft Windows Mobile (Pocket PC) based devices, despite an open-letter campaign to Sun to release a rumored internal implementation of PersonalJava known by the code name "Captain America".  Third party implementations like JBlend and JBed are widely used by Windows Mobile vendors like HTC and Samsung.
Operating systems targeting Java ME have been implemented by DoCoMo in the form of DoJa, and by SavaJe as SavaJe OS. The latter company was purchased by Sun in April 2007 and now forms the basis of Sun's JavaFX Mobile. The company IS2T provides a Java ME virtual machine (MicroJvm) for any RTOS and even with no RTOS (then qualified as baremetal). When baremetal, the virtual machine is the OS/RTOS: the device boots in Java. 
provides an open source (LGPL) implementation of an MIDP emulator. This is a Java Applet-based emulator and can be embedded in web pages.
The open-source Mika VM aims to implement JavaME CDC/FP, but is not certified as such (certified implementations are required to charge royalties, which is impractical for an open-source project). Consequently, devices which use this implementation are not allowed to claim JavaME CDC compatibility.
The linux-based Android operating system uses a proprietary version of Java that is similar, but not identical to Java Me. 
|J2ME Platform Specification|
|MIDP 3.0||Java ME 3.4 and earlier only, Last Specification for Mobile Phones, Java Language features as Java SE 1.3|
|CLDC 8||New in Java ME 8|
|MEEP 8||New in Java ME 8, Language feature as Java SE 8, for Internet of Everything devices|
|File Connection and PIM||File system, contacts, calendar, to-do|
|Wireless Messaging API (WMA)|
|Mobile Media API (MMAPI)||Audio, video, multimedia|
|Security and Trust Services|
|Mobile 3D Graphics||High level 3D graphics|
|Java Technology for the Wireless Industry (JTWI)||General|
|Wireless Messaging 2.0 (WMA)|
|Content Handler API|
|Scalable 2D Vector Graphics API for J2ME|
|Information Module Profile - Next Generation|
|Advanced Multimedia Supplements (AMMS)||MMAPI extensions|
|Mobile Internationalization API|
|Java Bindings for the OpenGL ES API|
|Mobile Service Architecture|
|Mobile Telephony API|
|Mobile Sensor API|
|Contactless Communication API|
|Mobile User Interface Customization API|
|Mobile Broadcast Service API for Handheld Terminals|
|XML API for Java ME|
|IMS Services API|
|Scalable 2D Vector Graphics API 2.0 for Java ME|
|Location API 2.0|
|Telematics API for Java ME|
|DRM API for Java ME|
|IMS Communication Enablers|
|Mobile 3D Graphics API (M3G) 2.0|
The ESR consortium is devoted to Standards for embedded Java. Especially cost effective Standards. Typical applications domains are industrial control, machine-to-machine, medical, e-metering, home automation, consumer, human-to-machine-interface, ...
|B-ON (Beyond CLDC)||B-ON serves as a very robust foundation for implementing embedded Java software. It specifies a reliable initialization phase of the Java device, and 3 kind of objects: immutable, immortal and regular (mortal) objects.|
|MicroUI||MicroUI defines an enhanced architecture to enable an open, third-party, application development environment for embedded HMI devices. Such devices typically have some form of display, some input sensors and potentially some sound rendering capabilities. This specification spans a potentially wide set of devices.|
|MWT||MWT defines three distinct roles: Widget Designers, Look and Feel Designers, and Application Designers. MWT allows a binary HMI application to run the same on all devices that provide a compliant MWT framework (embedded devices, cellphones, set-top box TV's, PC's, etc...) allowing for true consistency and ubiquity of applications across product lines (ME, SE, EE).|
|ECLASSPATH||ECLASSPATH unifies CLDC, CDC, Foundation, SE, and EE execution environments with a set of around 300 classes API. Compiling against CLDC1.1/ECLASSPATH makes binary code portable across all Java execution environments.|