This is a tutorial in which we will going to create a program that can download an image file or any files in a website using Java.


So, now let's start this tutorial!

1. Open JCreator or NetBeans and make a java program with a file name of imgFromURL.java.

2. Import the following packages:

1. import
   
   java.io.*
   
   ;
   
   //used to access the DataInputStream and FileOutputStream class that will get and save the file to the directory program
   
2. import
   
   java.net.*
   
   ;
   
   //used to access the URL and URL connection class to access websites
   

3. Initialize your variable in your Main, variable p for byte data type which will save memory in a large array since this data type is 4 times smaller than int data type and variable url for the URL class that will open the world wide web in a specific website as instantiated.

1. byte
   
   [
   
   ]
   
   b =
   
   new
   
   byte
   
   [
   
   1
   
   ]
   
   ;
   
2. URL
   
   url =
   
   new
   
   URL
   
   (
   
   "http://www.sourcecodester.com/sites/default/files/print_0.png"
   
   )
   
   ;
   

We access an image file as we have a png extension file from the sourcecodester site.

Now create a variable named urlConnect for the URLConnection class that we will open the connection using the openConnection method of the variable url above. And with the urlConnect variable, have its connect method to perform connectivity to the site. But take note that we will need the internet on this to download the file.

1. URLConnection
   
   urlConnect =
   
   url.openConnection
   
   (
   
   )
   
   ;
   
2. urlConnect.connect
   
   (
   
   )
   
   ;
   

3. Create now a variable di for our DataInputStream class to get the the inputted url from the URLConnection class.

1. DataInputStream
   
   di =
   
   new
   
   DataInputStream
   
   (
   
   urlConnect.getInputStream
   
   (
   
   )
   
   )
   
   ;
   

Now, to get the file we will use the FileOutputStream and have it instantiated with the name of the file to be saved. Have this code below:

1. FileOutputStream
   
   fo =
   
   new
   
   FileOutputStream
   
   (
   
   "print_0.png"
   
   )
   
   ;
   

4. To download the file, have this code below using the FileOutputStream, DataInputStream variable and the byte variable, then close the di and fo variable for streaming.

1. while
   
   (
   
   -
   
   1
   
   !=
   
   di.read
   
   (
   
   b, 0
   
   , 1
   
   )
   
   )
   
2. fo.write
   
   (
   
   b, 0
   
   , 1
   
   )
   
   ;
   
3. di.close
   
   (
   
   )
   
   ;
   
4. fo.close
   
   (
   
   )
   
   ;
   

Output:


Here's the full code of this tutorial:

1. import
   
   java.io.*
   
   ;
   
   //used to access the DataInputStream and FileOutputStream class that will get and save the file to the directory program
   
2. import
   
   java.net.*
   
   ;
   
   //used to access the URL and URL connection class to access websites
   
3. 
   
4. public
   
   class
   
   imgFromURL {
   
5. public
   
   static
   
   void
   
   main(
   
   String
   
   args[
   
   ]
   
   )
   
   throws
   
   Exception
   
   {
   
6. 
   
7. byte
   
   [
   
   ]
   
   b =
   
   new
   
   byte
   
   [
   
   1
   
   ]
   
   ;
   
   //data type to save memory space of the file
   
8. URL
   
   url =
   
   new
   
   URL
   
   (
   
   "http://www.sourcecodester.com/sites/default/files/print_0.png"
   
   )
   
   ;
   
   // url of the site that we will going to download the image file
   
9. 
   
10. URLConnection
    
    urlConnect =
    
    url.openConnection
    
    (
    
    )
    
    ;
    
11. urlConnect.connect
    
    (
    
    )
    
    ;
    
    // get the connection to the site
    
12. 
    
13. 
    
14. DataInputStream
    
    di =
    
    new
    
    DataInputStream
    
    (
    
    urlConnect.getInputStream
    
    (
    
    )
    
    )
    
    ;
    
    //have the input to the connection
    
15. 
    
16. FileOutputStream
    
    fo =
    
    new
    
    FileOutputStream
    
    (
    
    "print_0.png"
    
    )
    
    ;
    
    //download the file and have it named print_0.png
    
17. 
    
18. while
    
    (
    
    -
    
    1
    
    !=
    
    di.read
    
    (
    
    b, 0
    
    , 1
    
    )
    
    )
    
    //download the image file
    
19. fo.write
    
    (
    
    b, 0
    
    , 1
    
    )
    
    ;
    
20. di.close
    
    (
    
    )
    
    ;
    
    // close DataInputStream
    
21. fo.close
    
    (
    
    )
    
    ;
    
    // close FileOutputStream
    
22. }
    
23. }
    

Best Regards,

Engr. Lyndon Bermoy
IT Instructor/System Developer/Android Developer/Freelance Programmer

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