Importing Packages in java
In java, the import keyword used to import built-in and user-defined packages. When a package has imported, we can refer to all the classes of that package using their name directly.
The import statement must be after the package statement, and before any other statement.
Using an import statement, we may import a specific class or all the classes from a package.
🔔 Using one import statement, we may import only one package or a class.
🔔 Using an import statement, we can not import a class directly, but it must be a part of a package.
🔔 A program may contain any number of import statements.
Importing specific class
Using an importing statement, we can import a specific class. The following syntax is employed to import a specific class.
import packageName.ClassName;
Let's look at an import statement to import a built-in package and Scanner class.
package myPackage;
import java.util.Scanner;
public class ImportingExample {
public static void main(String[] args) {
Scanner read = new Scanner(System.in);
int i = read.nextInt();
System.out.println("You have entered a number " + i);
}
}
In the above code, the class ImportingExample belongs to myPackage package, and it also importing a class called Scanner from java.util package.
Importing all the classes
Using an importing statement, we can import all the classes of a package. To import all the classes of the package, we use * symbol. The following syntax is employed to import all the classes of a package.
import packageName.*;
Let's look at an import statement to import a built-in package.
package myPackage;
import java.util.*;
public class ImportingExample {
public static void main(String[] args) {
Scanner read = new Scanner(System.in);
int i = read.nextInt();
System.out.println("You have entered a number " + i);
Random rand = new Random();
int num = rand.nextInt(100);
System.out.println("Randomly generated number " + num);
}
}
In the above code, the class ImportingExample belongs to myPackage package, and it also importing all the classes like Scanner, Random, Stack, Vector, ArrayList, HashSet, etc. from the java.util package.
🔔 The import statement imports only classes of the package, but not sub-packages and its classes.
🔔 We may also import sub-packages by using a symbol '.' (dot) to separate parent package and sub-package.
Consider the following import statement.
import java.util.*;
The above import statement util is a sub-package of java package. It imports all the classes of util package only, but not classes of java package.