Skip to main content

Regarding class files

Class files:-Regarding class file or dot class file also known as byte code of class, in a java programming language we can use any number of classes in our program. After compilation all classes convert into individual .class file.

Example:-

class A
{
}
class B
{
}
class C
{
}
class Student
{
public static void main(String[]args)
{
System.out.println("Well-come to my java blog");
}
}

We can save above program to any classname.java or we can use any other name.java, there is no compulsion for java file name. But recommended to save by that class name which having main method.

I saved the above file to Student.java name. Before compilation my C:\JAVATECH folder contain only one java file.

Student.java

For  compilation.

C:\JAVATECH>javac  Student.java

After compilation my C:\JAVATECH folder contains five files, one java file as previous and four .class files.

Student.java
Student.class
A.class
B.class
C.class

For Run:-

C:\JAVATECH>java Student

Well-come to my java blog

If we save above program b y A.java name then no issue we can do this.

For  compilation.

C:\JAVATECH>javac  A.java

After that successfully program will compile and generate .class files same as above.

For Run:-

C:\JAVATECH>java A

Error: Main method not found in class A, please define the main method as:
   public static void main(String[] args).

Because jvm search main method in A.class file only.
So for successfully execution we have to use below commands.

C:\JAVATECH>javac  A.java
C:\JAVATECH>java Student

Well-come to my java blog

In the above program we can write main method in every class.

class A
{
public static void main(String[]args)
{
System.out.println("Well-come to my java blog  A class main method");
}

}
class B
{
public static void main(String[]args)
{
System.out.println("Well-come to my java blog  B class main method");
}

}
class C
{
public static void main(String[]args)
{
System.out.println("Well-come to my java blog C class main method");
}

}
class Student
{
public static void main(String[]args)
{
System.out.println("Well-come to my java blog Student class main method");
}
}

We can save above program by any class name or we can use any other name for (.java) file and run by any .class file because every class having main method. Suppose above program is saved by Test.java name.

C:\JAVATECH>javac Test (compile once only)
C:\JAVATECH>java Student

Well-come to my java blog Student class main method.

C:\JAVATECH>java A

Well-come to my java blog A class main method.

C:\JAVATECH>java B

Well-come to my java blog B class main method.

C:\JAVATECH>java C

Well-come to my java blog C class main method.



Labels:

Comments

Post a Comment

Popular posts from this blog

Inner classes

Inner Classes:- class inside class or interface called inner class or nested class. Advantage of inner classes is grouping multiple classes and interfaces into a single class. Another big advantage of inner class is that inner class can happily access all the data or variables of outer class directly. Types of Nested classes:- There are two types of nested classes static and non-static nested classes. (A)Non –static inner classes:- 1)     Member inner class 2)     Anonymous inner class 3)     Local inner class (B)Static nested class Example1:-Outer.java class Outer { class Inner { void disp() { System.out.println("Hello This is Inner class Method"); } } public static void main(String[]args) { Inner in=new Inner(); in.disp(); } } Output:- C:\JAVATECH>javac Outer.java Outer.java:12: error: non-static variable this cannot be referenced from a static context Inner in=new Inner(); ...
Post a Comment
Read more

Inheritance-4

Example10:- class Student { Student() { System.out.println("This is super class Zero argument constructor"); } Student(String s) { System.out.println("This is super class One argument constructor"); } } class Test extends Student { Test() { super(null); System.out.println("This is sub class Zero argument constructor"); } public static void main(String[]args) { Test t=new Test(); } } Output:- C:\JAVATECH>javac Test.java C:\JAVATECH>java Test This is super class One argument constructor This is sub class Zero argument constructor Example11:- class Student { Student() { System.out.println("This is super class Zero argument constructor"); } Student(String s) { System.out.println("This is super class One argument constructor"); } } class Test extends Student { Test() { super(); super(null); System.out.println("This is su...
Post a Comment
Read more

Small concept about OOPs

Some small concept about OOPs:- In many books and website write about OOPs concepts as hundred percent object oriented, pure object oriented and partial object oriented language. Hundred percent object oriented:- In the hundred percent object oriented movie hero is object, without object program is incomplete that means can not execute program without object. Without class and object programming or application development is not possible. Example of hundred percent object oriented language is  Smalltalk . Pure object oriented:- In the object oriented cinema obviously object is the hero. In pure object oriented language object having same importance but in this having some relax that is without creating object we can successfully execute our application. So in the object oriented programming without class we cannot create or run our application, class is must. Example of pure object oriented language is  Java . Partial object oriented:- In this type of la...
Post a Comment
Read more