Re: Difference between JDK1.4.2, JDK 1.5.0 and JDK1.6
JDK 1.0 (january 23, 1996) oak
- Initial release
JDK 1.1 (february 19, 1997)
- Retooling of the AWT event model
- Inner classes added to the language
- JavaBeans
- JDBC
- RMI
J2SE 1.2 (December 8, 1998) playground
This and subsequent releases through J2SE 5.0 were rebranded retrospectively Java 2 & 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).
- Strictfp keyword
- Reflection
- Swing api integration into the core classes
- JVM equipped with a jit compiler
- Java plug-in
- Java IDL
- An IDL implementation for corba interoperability
- Collections Framework
J2SE 1.3 (may 8, 2000) kestrel
- Hotspot jvm included
- JavaSound
- JNDI included in core libraries
- Java platform debugger architecture (jpda)
- RMI was modified to support optional compatibility with corba
J2SE 1.4 (february 6, 2002) merlin
- assert keyword
- 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)
- Logging API
- Image i/o api for reading and writing images in formats like jpeg and png
- Integrated XML parser and XSLT processor (JAXP)
- Integrated security and cryptography extensions (JCE, JSSE, JAAS)
- Java web start
J2SE 5.0 (september 30, 2004) tiger [originally numbered 1.5]
- Generics: provides compile-time (static) type safety for collections and eliminates the need for most typecasts (type conversion).
- 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.
- Autoboxing/unboxing: automatic conversions between primitive types (such as int) and primitive wrapper classes (such as integer).
- 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).
- Swing: new skinnable look and feel, called synth.
- Var args: 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, such as the standard collection classesfix the previously broken semantics of the java memory model, which defines how threads interact through memory.
- Automatic stub generation for rmi objects.
- Static imports concurrency utilities in package java.util.concurrent.
- Scanner class for parsing data from various input streams and buffers.
- Assertions
- StringBuilder class (in java.lang package)
- Annotations
Java SE 6 (december 11, 2006) mustang
sun replaced the name "J2SE" with java se and dropped the ".0" from the version number.
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 14 which was released in may 2009.
- Support for older win9x versions dropped.
- Scripting lang support: Generic API for integration with scripting languages, & built-in mozilla javascript rhino integration
- Dramatic performance improvements for the core platform, and swing.
- Improved web service support through JAX-WS JDBC 4.0 support
- Java compiler API: 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
- 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).
Java se 6 update 10
A major enhancement in terms of end-user usability.
- Java Deployment Toolkit, a set of javascript functions to ease the deployment of applets and java web start applications.
- Java Kernel, a small installer including only the most commonly used jre classes. Enhanced updater.
- Enhanced versioning and pack200 support: server-side support is no longer required.
- Java quick starter, to improve cold start-up time.
- Improved performance of java2D graphics primitives on windows, using direct3D and hardware acceleration.
- A new Swing look and feel called NIMBUS and based on synth.
- Next-generation java plug-in: applets now run in a separate process and support many features of web start applications.
Java se 6 update 12
This release includes the highly anticipated 64-bit java plug-in (for 64-bit browsers only), windows server 2008 support,
and performance improvements of java and JAVAFX applications.
J2SE 5.0 Features:
Import Static:
The static import declaration imports static members from classes, allowing them to be used without class qualification.
So when should you use static import? Very sparingly! Only use it when you'd otherwise be tempted to declare local copies of constants, or to abuse inheritance (the Constant Interface Antipattern). In other words, use it when you require frequent access to static members from one or two classes. If you overuse the static import feature, it can make your program unreadable and unmaintainable, polluting its namespace with all the static members you import. Readers of your code (including you, a few months after you wrote it) will not know which class a static member comes from. Importing all of the static members from a class can be particularly harmful to readability; if you need only one or two members, import them individually. Used appropriately, static import can make your program more readable, by removing the boilerplate of repetition of class names.
Example:
import static java.lang.System.out;
public class StaticImports
{
public static void main(String args[])
{
out.println("welcome");
}
}
Varargs in Java: Variable argument method in Java 5
I think I am late for writing about varargs. The feature of variable argument has been added in Java 5 since its launch. Still I will write something about varargs.
varargs has been implemented in many languages such as C, C++ etc. These functionality enables to write methods/functions which takes variable length of arguments. For example the popular printf() method in C. We can call printf() method with multiple arguments.
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Varargs was added in Java 5 and the syntax includes three dots … (also called ellipses). Following is the syntax of vararg method.
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Notice the dots … in above code. That mark the last argument of the method as variable argument. Also the vararg must be the last argument in the method.
Now let us check simple hello world varargs code.
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In above code, the test() method is taking variable arguments and is being called from main method with number of arguments.
So when should you use varargs? As a client, you should take advantage of them whenever the API offers them. Important uses in core APIs include reflection, message formatting, and the new printf facility. As an API designer, you should use them sparingly, only when the benefit is truly compelling. Generally speaking, you should not overload a varargs method, or it will be difficult for programmers to figure out which overloading gets called.
What is the difference between local variable, instance variable, and class variable and an example?
Instance Variables (Non-Static Fields) Technically speaking, objects store their individual states in "non-static fields", that is, fields declared without the static keyword. Non-static fields are also known as instance variables because their values are unique to each instance of a class (to each object, in other words); the currentSpeed of one bicycle is independent from the currentSpeed of another.
# Class Variables (Static Fields) A class variable is any field declared with the static modifier; this tells the compiler that there is exactly one copy of this variable in existence, regardless of how many times the class has been instantiated. A field defining the number of gears for a particular kind of bicycle could be marked as static since conceptually the same number of gears will apply to all instances. The code static int numGears = 6; would create such a static field. Additionally, the keyword final could be added to indicate that the number of gears will never change.
# Local Variables Similar to how an object stores its state in fields, a method will often store its temporary state in local variables. The syntax for declaring a local variable is similar to declaring a field (for example, int count = 0;). There is no special keyword designating a variable as local; that determination comes entirely from the location in which the variable is declared — which is between the opening and closing braces of a method. As such, local variables are only visible to the methods in which they are declared; they are not accessible from the rest of the class.
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