Monthly Archives: May 2014

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The new lambda expressions included in Java Platform Standard Edition 8 (Java SE 8).

Lambda expressions are a new and important feature included in Java SE 8. They provide a clear and concise way to represent one method interface using an expression. Lambda expressions also improve the Collection libraries making it easier to iterate through, filter, and extract data from a Collection. In addition, new concurrency features improve performance in multicore environments.

The following is a list of hardware and software requirements:

  • Java Development Kit (JDK 8) early access
  • NetBeans 7.4

Lambda Expression Syntax

Lambda expressions address the bulkiness of anonymous inner classes by converting five lines of code into a single statement. This simple horizontal solution solves the "vertical problem" presented by inner classes.

A lambda expression is composed of three parts.

Argument List Arrow Token Body
(int x, int y) -> x + y

The body can be either a single expression or a statement block. In the expression form, the body is simply evaluated and returned. In the block form, the body is evaluated like a method body and a return statement returns control to the caller of the anonymous method. The break and continue keywords are illegal at the top level, but are permitted within loops. If the body produces a result, every control path must return something or throw an exception.

Example

Here is how you write a Runnable using lambdas.

 6 public class RunnableTest {
 7   public static void main(String[] args) {
 8     
 9     System.out.println("=== RunnableTest ===");
10     
11     // Anonymous Runnable
12     Runnable r1 = new Runnable(){
13       
14       @Override
15       public void run(){
16         System.out.println("Hello world one!");
17       }
18     };
19     
20     // Lambda Runnable
21     Runnable r2 = () -> System.out.println("Hello world two!");
22     
23     // Run em!
24     r1.run();
25     r2.run();
26     
27   }
28 }

In both cases, notice that no parameter is passed and is returned. The Runnable lambda expression, which uses the block format, converts five lines of code into one statement.

Reference Source for this information is www.oracle.com

 

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Java8 has been released with a many new features and no doubt these new features are very useful and very interesting to use such as Lambda expressions.

So have a look on java 8's features :

Lambda Expressions 

Lambda Expressions, a new language feature, has been introduced in this release.They enable you to treat functionality as a method argument, or code as data. Lambda expressions let you express instances of single-method interfaces (referred to as functional interfaces) more compactly.

Methods References

Method references provide easy-to-read lambda expressions for methods that already have a name.

New Api for Date and Time 

A new set of packages that provide a comprehensive date-time model.

New Stream Api

Improved Type Interface

Method parameter References

Repeating Annotations 

Repeating Annotations provide the ability to apply the same annotation type more than once to the same declaration or type use.

Type Annotations

Type Annotations provide the ability to apply an annotation anywhere a type is used, not just on a declaration. Used with a pluggable type system, this feature enables improved type checking of your code.

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Java programming language support these primitive data types:

1. Byte : It is equals to 8 bits

2. Short : (16 bits equals to two bytes)

3. Int : (32 bits equals to 4 bytes)

4. Long : (64 bits equals to 8 bytes)

5. Boolean : Has to possible values either True or False

6. Char :Store a single char

7. Float : (32 bits equals to 4 bytes)

8. Double : (64 bits equals to 8 bytes)

All these data types considered as reserved keywords pre defined by programming language  . Primitive values cannot share its state with other primitive values. primitive data types are not object that why we do not use new keyword. There are default values for above types are:

default values

 

primitive data types

primitive data types

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I am going to start with a basic description for java variables because variables in any language are very useful works as a building block for any program , so lets start...

First of all What is meaning of word variable it means not having a fixed pattern. Its a container hold a value for u ,  When we define a variable with value at beginning of  any program after some code we can change  value of that variable , of course there are lots of other benefits of variables in java ....so we will describe later.

A variable is also called field so do not confuse . In java we can define  variables as :

1. Instance variables

2. Class variables

3. Local variables

1. Instance variables : A variables which also called non static field define with out static keyword and value of instance variable are unique for each instance of a class.

Note : you can not use instance variable in static method till you can not create a object of that class having instance variable.

2. Class variables : A variable with static modifier and value of a static field is same in all over code and we use it by class name do not need to create object.

3. Local variablesA variable only visible to the method where they are declared , no any use of special keyword with local variables.

How we can use these variables:

first we have to define datatype then name of variable end with semicolon like:

int varA ;

now you can assign value to variable here e.g: int varA = 10; or you can assign value where ever you want in code. The advantage of java variable are that we can define and declare a variable any where in the code unlike C.

Working with variables

Working with variables