Keywords are important in any programming language. In java, we classified the keywords in many categories.
In part1 of
blog post explains the first two categories of keywords. The link is given below.
https://rajeeva84.blogspot.com/2024/08/keywords-in-java-part-1.html
Here,
remaining keywords and its usage are explained with examples.
3. Keywords
based on objects and classes:
Classes are the non-primitive
datatypes. Each java program should start with a class. The class name is the file
name where the main () function resides.
Object is a
real-world entity. The keywords related to classes and objects are listed
below.
|
abstract |
extends |
instanceof |
return |
synchronized |
transient |
|
this |
void |
static |
public |
private |
protected |
|
super |
sealed |
permits |
native |
new |
null |
Abstract:
It deals with
abstract classes and methods. This deals with defining a class or function for
abstraction.
void: It represents that the function
doesn’t return anything.
These are
declared, but not defined. These class and function can be inherited by other
class and define the functions.
Extends:
It deals
with sub class. The child class extends the methods from parent class.
Eg: use the
previous abstract class as parent.
new: it is used to create new object.
instanceof
: It is used to
check the object reference. If it is true, the object exists.
return: This returns the value.
synchronized:
It deals with multithreading.
When multiple threads share one resource, this block helps you to access. A
sample block is given below.
synchronized(sync_object)
{
//statements
to access variables and resources
}
transient: It is defined for
variable, which is used in serialization.
this: it denotes the current object
instance.
static: The value is retained across the program.
public: It is a access specifier. The member
can be accessed by all( parent and child classes)
protected: This is used to access its parent
and member functions.
private: This can be accessed by same class
only.
super: It deals with base class.
sealed: It is introduced in java15.It is
sealed. Unless otherwise it cannot be accessed without permits option.
native: It is defined by JNI(Java Native
Interface). It is applicable for methods only.
null: it represents null value.
let us code
an Example with some keywords:
abstract
class abc
{
abstract void display();
}
class def extends abc {
void
display()
{
System.out.println(“Welcome
to the world of java”);
}
}
class ghi
{
public static
void main(String args[])
{
abc a = new
def();
a.display();
System.out.println(object instanceof abc);
}
}
4. Keywords based on exceptions:
Java is excellent in error handling. These are
keywords used.
|
try |
catch |
final |
finally |
This is the
syntax given below.
try and
catch :
try
{
}catch(Exception
e)
{
}
final and
finally:
try
{
final a;
}
finally()
{
}
5. Others:
These are the other keywords listed below.
|
assert |
enum |
interface |
package |
assert:It is a statement executed when assert function is called.
Eg:
Assert a > b : “a is the biggest number”;
enum: It represents a collection of named objects.
Eg:
Enum a {
1,2,3;}
interface : It is like a blueprint of class and
functions behavior.
Eg:
Interface f1
{
final int s;
void a();
}
package : It is a collection of classes and objects.
Eg: package a; //user defined package.
Import java.io.*; //built in package.
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