The Java language has undergone several changes since JDK 1.0 as well as numerous additions of classes and packages to the standard library. Since J2SE 1.4, the evolution of the Java language has been governed by the Java Community Process (JCP), which uses Java Specification Requests (JSRs) to propose and specify additions and changes to the Java platform. The language is specified by the Java Language Specification (JLS); changes to the JLS are managed under JSR 901.
In addition to the language changes, much more dramatic changes have been made to the Java class library over the years, which has grown from a few hundred classes in JDK 1.0 to over three thousand in J2SE 5000 Entire new APIs, such as Swing and Java2D, have been introduced, and many of the original JDK 1.0 classes and methods have been deprecated.
JDK 1.0 (January 23, 1996)
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Codename Oak. Initial release the first stable version was the JDK 1.0.2. is called Java 1
JDK 1.1 (February 19, 1997)
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Major additions included:
- an extensive retooling of the AWT event model
- inner classes added to the language
- JavaBeans
- JDBC
- RMI
- Reflection which supported Introspection only, no modification at runtime was possible.
J2SE 1.2 (December 8, 1998)
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Codename Playground. This and subsequent releases through J2SE 5.0 were rebranded retrospectively Java 2 and the version name "J2SE" (Java 2 Platform, Standard Edition) replaced JDK to distinguish the base platform from J2EE (Java 2 Platform, Enterprise Edition) and J2ME (Java 2 Platform, Micro Edition). Major additions included:
- strictfp keyword
- the Swing graphical API was integrated into the core classes
- Sun's JVM was equipped with a JIT compiler for the first time
- Java Plug-in
- Java IDL, an IDL implementation for CORBA interoperability
- Collections framework
J2SE 1.3 (May 8, 2000)
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Codename Kestrel. The most notable changes were:
- HotSpot JVM included (the HotSpot JVM was first released in April, 1999 for the J2SE 1.2 JVM)
- RMI was modified to support optional compatibility with CORBA
- JavaSound
- Java Naming and Directory Interface (JNDI) included in core libraries (previously available as an extension)
- Java Platform Debugger Architecture (JPDA)
- Synthetic proxy classes
J2SE 1.4 (February 6, 2002)
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Codename Merlin. This was the first release of the Java platform developed under the Java Community Process as JSR 59. Major changes included:
- assert keyword (Specified in JSR 41.)
- regular expressions modeled after Perl regular expressions
- exception chaining allows an exception to encapsulate original lower-level exception
- Internet Protocol version 6 (IPv6) support
- Non-blocking NIO (New Input/Output) (Specified in JSR 51.)
- logging API (Specified in JSR 47.)
- image I/O API for reading and writing images in formats like JPEG and PNG
- integrated XML parser and XSLT processor (JAXP) (Specified in JSR 5 and JSR 63.)
- integrated security and cryptography extensions (JCE, JSSE, JAAS)
- Java Web Start included (Java Web Start was first released in March, 2001 for J2SE 1.3) (Specified in JSR 56.)
- Preferences API (java.util.prefs)
J2SE 5.0 (September 30, 2004)
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Codename Tiger. Originally numbered 1.5, which is still used as the internal version number. This version was developed under JSR 176.
J2SE 5.0 entered its end-of-life on April 8, 2008 and is no longer supported by Sun as of November 3, 2009.
Tiger added a number of significant new language features:
- Generics: Provides compile-time (static) type safety for collections and eliminates the need for most typecasts (type conversion). (Specified by JSR 14.)
- Metadata: Also called annotations; allows language constructs such as classes and methods to be tagged with additional data, which can then be processed by metadata-aware utilities. (Specified by JSR 175.)
- Autoboxing/unboxing: Automatic conversions between primitive types (such as int) and primitive wrapper classes (such as Integer). (Specified by JSR 201.)
- Enumerations: The enum keyword creates a typesafe, ordered list of values (such as Day.MONDAY, Day.TUESDAY, etc.). Previously this could only be achieved by non-typesafe constant integers or manually constructed classes (typesafe enum pattern). (Specified by JSR 201.)
- Swing: New skinnable look and feel, called synth.
- Varargs: The last parameter of a method can now be declared using a type name followed by three dots (e.g. void drawtext(String... lines)). In the calling code any number of parameters of that type can be used and they are then placed in an array to be passed to the method, or alternatively the calling code can pass an array of that type.
- Enhanced for each loop: The for loop syntax is extended with special syntax for iterating over each member of either an array or any Iterable
- Fix the previously broken semantics of the Java Memory Model, which defines how threads interact through memory.
- Automatic stub generation for RMI objects.
- Static imports
- Java 5 is the last release of Java to officially support the Microsoft Windows 9x line (Windows 95, Windows 98, Windows ME). Unofficially, Java SE 6 Update 7 (1.6.0.7) is the last version of Java to be shown working on this family of operating systems.
- The concurrency utilities in package java.util.concurrent.
- Scanner class for parsing data from various input streams and buffers.
Java SE 6 (December 11, 2006)
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Codename Mustang. As of this version, Sun replaced the name "J2SE" with Java SE and dropped the ".0" from the version number. Internal numbering for developers remains 1.6.0.This version was developed under JSR 270.
During the development phase, new builds including enhancements and bug fixes were released approximately weekly. Beta versions were released in February and June 2006, leading up to a final release that occurred on December 11, 2006. The current revision is Update 24 which was released in February 2011.
Major changes included in this version:
- Support for older Win9x versions dropped. Unofficially Java 6 Update 7 is the last release of Java shown to work on these versions of Windows. This is believed to be due to the major changes in Update 10.
- Scripting Language Support (JSR 223): Generic API for tight integration with scripting languages, and built-in Mozilla JavaScript Rhino integration
- Dramatic performance improvements for the core platform, and Swing.
- Improved Web Service support through JAX-WS (JSR 224)
- JDBC 4.0 support (JSR 221).
- Java Compiler API (JSR 199): an API allowing a Java program to select and invoke a Java Compiler programmatically.
- Upgrade of JAXB to version 2.0: Including integration of a StAX parser.
- Support for pluggable annotations (JSR 269)
- Many GUI improvements, such as integration of SwingWorker in the API, table sorting and filtering, and true Swing double-buffering (eliminating the gray-area effect).
- JVM improvements include: synchronization and compiler performance optimizations, new algorithms and upgrades to existing garbage collection algorithms, and application start-up performance.
Java SE 7
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Java 7 (codename Dolphin) is an upcoming major update to Java. The development period is organized into thirteen milestones; on February 18, 2011, milestone 13, the last milestone was reached. Multiple builds, which generally include enhancements and bug fixes, are released per milestone. The Feature list at the Open JDK 7 project lists many of the expected feature changes.
The expected feature additions for Java 7
- JVM support for dynamic languages, following the prototyping work currently done on the Multi Language Virtual Machine
- Compressed 64-bit pointers
- Language changes under Project Coin. The features accepted for inclusion in Project Coin are:
- Strings in switch
- Automatic resource management
- Improved Type Inference for Generic Instance Creation
- Simplified Varargs Method Invocation
- Better integral literals allowing for underscores as digit separators
- Language-level support for Collections
- Concurrency utilities under JSR 166
- New file I/O library to enhance platform independence and add support for metadata and symbolic links. The new packages are java.nio.file and java.nio.file.attribute
- Library-level support for Elliptic curve cryptography algorithms
- An XRender pipeline for Java 2D, which improves handling of features specific to modern GPUs
- New platform APIs for the graphics features originally planned for release in Java version 6u10
- Enhanced library-level support for new network protocols, including SCTP and Sockets Direct Protocol
- Upstream updates to XML and Unicode
Java SE 8
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Java 8 is expected in late 2012 and will include at a minimum the features that were planned for Java 7 but later deferred.
- Modularization of the JDK under Project Jigsaw
- Language-level support for lambda expressions (officially, lambda expressions; unofficially, closures) under Project Lambda. There was an ongoing debate in the Java community on whether to add support for lambda expressions. Sun later declared that lambda expressions would be included in Java 7 and asked for community input to refine the feature.
- Parts of project Coin that are not included in Java 7
I will post soon on J2SE 1.4 (Merlin), J2SE 5.0 (tiger) and Java SE 6 (mustang) features
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