Java Blocks

Blocks in java

Block: A set of statements together is called as block. The set of statements are written inside the flower braces {}.

In java there are two types of Blocks they are :

  1. Instance Block.
  2. Static block.
Instance Block: Instance block is a set of statements written within the flower braces and will execute when an object is created . Instance blocks will not have any name. Instance blocks will completely depends on the object of a class created .

Syntax:

{
    set of statements;
}

Program Using Instance Block


class InstanceBlock
{
InstanceBlock()
{
System.out.println("Location Of Institute : Dilsuknagar");
}
//Instance Block
{
System.out.println("Name Of Institute : Void Main Technologies");
}

}
class InstanceBlockTest
{
public static void main(String[] args) 
{
InstanceBlock ib=new InstanceBlock();
}
}

Save as:

InstanceBlockTest.java

Compile:

javac InstanceBlockTest.java

Run:

java InstanceBlockTest

Output:

Name Of Institute :void Main Technologies

Location Of Institute : Dilsuknagar

Note:
  1. In any program instance block will be executed first later constructor will be executed .
  2. If we have inheritance concept then first super class instance block will be executed then super class constructor will be executed and later sub class block and sub class constructor will be executed. 

Static Block: This blocks will be executed first in the program without depending on the instance of the class. Static block statements are written inside the static block .This block can be defined by using static keyword .

Syntax:

static
{
     set of statements;
}

Program Using Static Block


class StaticBlock
{
StaticBlock()
{
System.out.println("Location of institute : Dilsuknagar");
}
//Instance Block
{
System.out.println("Caption of Institute: For All Technical courses");
}
//Static Block
static
{
System.out.println("Name Of Institute: Void Main Technologies");
}

}
class StaticBlockTest 
{
public static void main(String[] args) 
{
StaticBlock sb=new StaticBlock();
}
}

Save as:

StaticBlockTest.java

Compile:

javac StaticBlockTest.java

Run:

java StaticBlockTest

Output:

Name Of Institute :void Main Technologies

 Caption of Institute: For All Technical courses

Location Of Institute : Dilsuknagar

Note:

Static block will be executed first in any program then the priority is for instance block and then constructor will be executed .We can run the program even without a main method using Static block. 

 Priority of execution is: 
Static block > instance Block > Constructor 


Program Using Static Block Without "main" method



 class StaticBlock
{
static
{
System.out.println("Name Of Institute: Void Main Technologies");

 System.out.println("Location Of Institute: Dilsuknagar");

 System.exit(0);

}
}
Save as:

StaticBlock.java

Compile:

javac StaticBlock.java

Run:

java StaticBlock

Output:

Name Of Institute :void Main Technologies

Location Of Institute : Dilsuknagar

Note:



Above program can be used to say that a program can execute even without main method.

Comments

Post a Comment

Popular posts from this blog

Programs on Inheritance

Image
Inheritance Inheritance is creating the object for one class and acquiring the properties of the parent object . Main theme of inheritance is code reusability . Types of inheritance in java : Single Inheritance. Multilevel Inheritance. Hierarchical Inheritance. Multiple Inheritance. Hybrid Inheritance. Note: Java does not support Multiple and  Hierarchical Inheritance using classes and can be supported using interfaces . Extends is the keyword to perform any type of inheritance. 1.Single Inheritance is a type of inheritance where one child class inherit the properties of one parent class. Programs on Single Inheritance class SingleInheritance  { String nameOfInstitute; String location; public void insertData(String nameOfInstitute,String location) { this.nameOfInstitute=nameOfInstitute; this.location=location; } } class SingleInheritanceTest extends SingleInheritance { public void pr...
Read more

Arrays In Java

Arrays In Java Arrays: It can be defined as the collection of similar elements together . Array Size Starts from "0" and ends at "n-1" Example:  Collection of student roll numbers comes under one single integer array. Collection of student names comes under one single String array. Collection of Faculty salarys comes under one single Float array. Types Of Arrays: There are three types of arrays they are : One/Single dimensional array Two Dimensional array Multi Dimensional array 1.One/Single Dimensional Array: One Dimensional array is used to collect the set of elements together . The Size of the array can be defined as "Product of number of bytes of datatype and size of the array."  Size of an array= number of bytes used by datatype * size of the array. Syntax: Initializing an array: <datatype>[] variable={values}; Example for initializing : int[] a={10,20,30,40}; Declaring an array: ...
Read more

Java Basics

Image
 Founder of java :  Games Gosling . In this section let us learn about: 1.Features of Java. 2. Architecture of JVM 3.Structure of Java  4.A Simple Java Program    1.Features of java 1.Simple:                       As it contains API documentation in clear and understandable way we can easily  reuse the code and syntax from java API which was given by   Sun Micro-system      2.Platform independent:                                                   java language can run on any type of platform (i.e.. windows,unix, linux, Mac e.c.t) and the output will be same .Hence java can referred as "WRITE ONCE AND USE ANYWHERE". 3.Object oriented :                        ...
Read more