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Sunday, 23 March 2014

Keywords in Java

We have already learnt about the keywords defination , different keywords and some important points about it in the previous post about Keywords and Identifiers in Java.
Now , after seeing all that keywords you must be feeling What do they do ? or What are their functions. In this post , we have put all the functions of all the 50 keywords in a tabular format.

                               Table of Keywords and their descriptions :-
                                  (-Each type is arranged alphabetically-)
Class ,Method and Variables modifiers
1.        abstract
Used to declare a class or method to be abstract. It signifies something empty. It is used to declare a class or method without any implementation. Object of a abstract class cannot be instantiated ,but can be extended by other classes.
2.        class
Used to define a class.
We have discussed class in detail. Click here.
3.        enum
Used to declare an enumerated type.
4.        extends
Used in sub-class declaration to specify the super class/parent class to the sub-class.
5.        final
Used to define an entity that cannot be changed or extended later.
6.        implements
Used in class declaration to specify one or more interfaces that are implemented by the current class.
7.        interface
Used to declare a special type of class that only contains abstract methods, constant fields which are static or final and static interfaces.
8.        native
Used to show that the implementation is not done in the same source file and ,also , it is in different language.
9.        new
Used for object creation and providing memory to it , generally , on heap.
10.     static
Used to declare a method, field or inner class as class members rather object members.
11.     strictfp
Used to ensure portability by restricting the precision and rounding of floating points in Java.
12.     synchronized
Used to ensure that at a time only one thread can be accessed by a method by using mutex lock.
13.     transient
Used to prevent fields from being serialized. Transient fields are always skipped when objects are serialized.
14.     volatile
Indicates that a variable may be modified by concurrently running threads. It can also be called as a lock-free mechanism.
Flow Control
15.     break
Used to exit the current enclosing block or skip the immediate statement. Actually , it transfers the flow of program to the other part of program.
16.     case
Used within switch statements. It executes a block of code depending on the switch expression .
17.     continue
Used to resume program execution at the end of the current loop body.
18.     default
Used within the switch statement. Executes a block of code , if none of the value of case keywords is matching with the switch statement value.
19.     do
Executes a block of code one time and then based on the while statement determines will that block of code be executed again.
20.     else
Executes a block of code when the if condition is not true.
21.     for
Used to define a loop that reiterates statements. The for loop specifies the statements to be executed , exit condition , updating operations and  initialization variables for the loop.
*A new concept of "enhanced for loop" has been specified where each iteration of the loop executes block of code using a different element in the array or Iterable.
22.     if
Used to a conditional test and executes a block of code if the test evaluates to true . If it evaluates to false , an optional block of code is defined with the else keyword .
23.     instanceof
Used to check an object belongs to which class. The instanceof evaluates to true if an object belongs to a specified class or its super class; else raises compilation error.
24.     return
Used to finish the execution of method. It can be followed by a value to pass to the caller method.
25.     switch
Used to evaluate a variable that can later be matched with a value specified by the case keyword in order to execute a block of statements.
26.     while
Used to execute a block of code in loop if given logical boolean  expression evaluates to true.
Special Reference
27.     super
Reference variable referring to immediate super class / parent class.
28.     this
Reference variable referring to the instance of current object.
Access Modifiers
29.     private
Used to make method or variable accessible only within its own class.
30.     protected
Used to make method or variable accessible only  to classes in same package or to subclasses(derived class) of the class.
31.     public
Used to make method or variable accessible to everybody.

32.     boolean
Used with variable that can have value as true or false only.
33.     byte
An 8-bit signed integer.
34.     char
An Unicode character(16-bit unsigned integer).
35.     double
An 64-bit signed floating-point number.
36.     float
An 32-bit signed floating-point number.
37.     int
An 32-bit signed integer.
38.     long
An 64-bit signed integer.
39.     short
A 16-bit integer value
Error Handling
40.     assert
Evaluates a conditional expression to verify the programmer’s assumption. If the condition is not true, an AssertionError is thrown. Generally used for debugging purpose.
41.     catch
Declares a block of code that executes if exception occurs .
42.     finally
Block of code that follows try block code and executes no matter how exception is handled.
43.     throw
Used to pass an exception to method that called this method

44.     throws
Used to specify which exceptions are not handled in the method and will be passed on to the next higher level of the program.
45.     try
Used with the block of code that will be tried for execution, but which may cause an exception.
Package Control
46.     import
Used at the beginning of a source file to declare what packages or classes are to imported.
47.     package
Used to keep classes together which have a relation between them.
Void keyword
48.     void
Used to indicate that the method does not have a return type.
Keywords unused
49.     const
Not used. 'final' keyword can be used in place of this keyword.
50.     goto
Not used.

So we have learnt the functions of all the 50 keywords present in Java programming langauge.
Don't worry , if you did not understand the meaning of all the above stuff. We will be learning the working of all of them as and when they come in further programs.


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  1. Great Explanation of keywords in Java .Thanks !!

    1. Thanks !! Keep Following JavaCompile for more stuff.


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