A package is a collection of related classes.
It helps Organize your classes into a folder structure and make it easy to locate and use them.
More importantly,It helps improve re-usability.
Syntax:-
package <package_name>;
The following video takes you through the steps of creating a package.
Assignment 1:To create a package
Step 1) Copy the following code into an editor
It helps Organize your classes into a folder structure and make it easy to locate and use them.
More importantly,It helps improve re-usability.
Syntax:-
package <package_name>;
The following video takes you through the steps of creating a package.
Assignment 1:To create a package
Step 1) Copy the following code into an editor
package p1;
class c1{
public void m1(){
class c1{
public void m1(){
System.out.println("Method m1 of Class c1");
}
public static void main(String args[]){
c1 obj = new c1();
obj.m1();
}
}
Step 2) Save the file as Demo.java. Compile the file as, javac – d . Demo.java
Step 3) Run the code as java p1.c1
Assignment 2) To create a sub-package
Step1) Copy the following code into an editor
package p1.p2;
}
public static void main(String args[]){
c1 obj = new c1();
obj.m1();
}
}
Step 2) Save the file as Demo.java. Compile the file as, javac – d . Demo.java
Step 3) Run the code as java p1.c1
Assignment 2) To create a sub-package
Step1) Copy the following code into an editor
package p1.p2;
class c2
{
public void m2(){
System.out.println("Method m2 of Class c2");
public void m2(){
System.out.println("Method m2 of Class c2");
}
public static void main(String args[]){
c2 obj = new c2();
obj.m2();
}
}
Step 2) Save the file as Demo2.java. Compile the file as javac – d . Demo2.java
Step 3) Run the code as java p1.p2.c2
importing a package
To create an object of a class (bundled in a package), in your code, you have to use its fully qualified name.
Ex.
java.awt.event.actionListner object = new java.awt.event.actionListner();
But , it could become tedious to type in the long dot-separated package path name for every class you want to use. Instead it is recommended you use the import statement.
Syntax
public static void main(String args[]){
c2 obj = new c2();
obj.m2();
}
}
Step 2) Save the file as Demo2.java. Compile the file as javac – d . Demo2.java
Step 3) Run the code as java p1.p2.c2
importing a package
To create an object of a class (bundled in a package), in your code, you have to use its fully qualified name.
Ex.
java.awt.event.actionListner object = new java.awt.event.actionListner();
But , it could become tedious to type in the long dot-separated package path name for every class you want to use. Instead it is recommended you use the import statement.
Syntax
import <package_name>;
Once imported , you can use the class without mentioning its fully qualified name.
Ex:
import java.awt.event.*; // * signifies all classes in this package
import javax.swing.JFrame // here only the JFrame class is imported
//Usage
JFrame f = new JFrame; // without fully qualified name.
Assignment 3: To import package
Step 1) Copy the code into an editor.
// Using packages created in earlier assignment
package p3;
import p1.*; //imports classes only in package p1 and NOT in the sub-package p2
class c3{
public void m3(){
System.out.println("Method m3 of Class c3");
}
public static void main(String args[]){
c1 obj1 = new c1();
obj1.m1();
p1.p2.c2 obj2 = new p1.p2.c2();
obj2.m2();
}
}
Step 2) Save the file as Demo2.java . Compile the file using the command javac –d .Demo2.java
Step3) Execute the code using the command java p3.c3
Packages - points to note:
To avoid naming conflicts packages are given names of the domain name of the company in reverse Ex : com.guru99. com.microsoft, com.infosys etc.
When a package name is not specified , a class is into the default package (the current working directory) and the package itself is given no name. Hence you were able to execute assignments earlier.
While creating a package, care should be taken that the statement for creating package must be written before any other import statements
// not allowed
import package p1.*;
package p3;
//correct syntax
package p3;
import package p1.*;
Once imported , you can use the class without mentioning its fully qualified name.
Ex:
import java.awt.event.*; // * signifies all classes in this package
import javax.swing.JFrame // here only the JFrame class is imported
//Usage
JFrame f = new JFrame; // without fully qualified name.
Assignment 3: To import package
Step 1) Copy the code into an editor.
// Using packages created in earlier assignment
package p3;
import p1.*; //imports classes only in package p1 and NOT in the sub-package p2
class c3{
public void m3(){
System.out.println("Method m3 of Class c3");
}
public static void main(String args[]){
c1 obj1 = new c1();
obj1.m1();
p1.p2.c2 obj2 = new p1.p2.c2();
obj2.m2();
}
}
Step 2) Save the file as Demo2.java . Compile the file using the command javac –d .Demo2.java
Step3) Execute the code using the command java p3.c3
Packages - points to note:
To avoid naming conflicts packages are given names of the domain name of the company in reverse Ex : com.guru99. com.microsoft, com.infosys etc.
When a package name is not specified , a class is into the default package (the current working directory) and the package itself is given no name. Hence you were able to execute assignments earlier.
While creating a package, care should be taken that the statement for creating package must be written before any other import statements
// not allowed
import package p1.*;
package p3;
//correct syntax
package p3;
import package p1.*;
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