Java.net.URLDecoder class in Java

Last Updated : 16 Jun, 2017

This is a utility class for HTML form decoding. It just performs the reverse of what URLEncoder class do, i.e. given an encoded string, it decodes it using the scheme specified. Generally when accessing the contents of request using getParameter() method in servlet programming, the values are automatically decoded before they are returned. But sometimes there may be a need to explicitly decode an otherwise URL encoded string.
The following steps are followed while decoding the strings:

Alphanumeric characters and certain special characters such as ‘*‘, ‘_‘, ‘–‘ and ‘.‘ remains unchanged.
‘+‘ signs are converted into spaces.
All other characters are decoded using the encoding scheme specified. The string of the form %xy, is converted to the character whose encoding would have resulted in this three character representation. W3C recommends using “UTF-8” for encoding purposes.

For example, the encoded string

u%40geeks+for+geeks

will be converted into the string representation where %40 will be replaced by an @ symbol and + signs are converted into space characters.

u@geeks for geeks

Methods :

decode() :

Syntax :public static String decode(String s)- @Deprecated
Parameters :
s : encoded string to be decoded

Syntax :public static String decode(String s,
            String enc)
                     throws UnsupportedEncodingException
Parameters : 
s : string to be decoded
enc : encoding to be used
Throws :
UnsupportedEncodingException : If the specified encoding is not used

Java Implementation :

// Java program to show decode() method of  
// URLDecoder class 
import java.io.UnsupportedEncodingException; 
import java.net.URLDecoder; 
  
public class urlDecoder  
{ 
    public static void main(String[] args)  
                             throws UnsupportedEncodingException  
    { 
        // encoded string 
        String encodedString = "u%40geeks+for+geeks"; 
        System.out.println("Encoded String :"); 
        System.out.println(encodedString); 
          
        // decode() method 
        System.out.println("Decoded String :"); 
        System.out.println(URLDecoder.decode(encodedString, "UTF-8")); 
    } 
} 

Output :

Encoded String :
u%40geeks+for+geeks
Decoded String :
u@geeks for geeks

References :
Official Java Documentation

java.net.URLConnection Class in Java

Rishabh Mahrsee

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Article Tags :

Java

Practice Tags :

Java

Java.net.URLDecoder class in Java

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