06 Aug Java Packages
A Package in Java, as the name suggests, groups related types i.e., it can be a group of related classes or related interfaces, etc. We already have built-in packages in Java, but we can also create our own packages to group related classes.
The following are some built-in Java packages:
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java.util java.io java.lang java.time java.math |
To import the entire package, use the import keyword:
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import java.util.* ; import java.io.* ; import java.lang.* ; import java.time.* ; import java.math.* ; |
User-defined Package
Let us now learn how to create a user-defined package in Java. Create a file in D: drive:
The package keyword will be used in our Java program to use the package:
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package amitpackage; |
Let us create Demo.java:
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package amitpackage; class Demo { public static void main(String[] args) { System.out.println("Our Demo class..."); } } |
Now, compile the file Demo.java:
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D:\ > javac Demo.java |
Compile the package:
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D:\ > javac -d . Demo.java |
The screenshot displays the same command:
Now, a new folder amitpackage will get created. Here’s the screenshot:
Run the Demo.java:
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D:\ > java amitpackage.Demo |
The above file will run successfully and now a class file will be visible in the amitpackage:
Also, the output “Our Demo class” will be visible on cmd:
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