Java Base64 Encode and Decode

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  To encrypt data at each level, this class provides three different encoders and decoders. At the following levels, these techniques are applicable.
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  1.Basic Encoding and Decoding
• 2.URL and Filename Encoding and Decoding
• 3.MIME

Basic Encoding and Decoding

Encoding and decoding are processes of converting data from one format to another.Data that has been encoded is converted back into its original form after being transmitted or stored through the process of decoding. Data conversion into a format suitable for transmission or storage is known as encoding.

The American Standard Code for Information Interchange (ASCII), one of the most popular encoding methods, assigns numerical values to each character in the English alphabet as well as to other symbols and control characters.

As an example , in ASCII, the letter "A" is given the decimal value of 65 and the letter "a" is given the decimal value of 97.The entire ASCII character set can be found in a table, which shows the decimal value assigned to each character.

Encoding :

Suppose we want to encode the message "Hello, World!" in ASCII. We would first convert each character in the message to its corresponding ASCII value using the ASCII table. The resulting encoded message would be: 72 101 108 108 111 44 32 87 111 114 108 100 33.

Each number in this encoded message represents the ASCII value of the corresponding character in the original message.

Decoding :

To decode the encoded message back into its original form, we would simply convert each ASCII value back into its corresponding character using the ASCII table. The resulting decoded message would be: Hello, World!

By converting the ASCII values back into their corresponding characters, we have successfully decoded the original message.

Java Example of Basic Encoding and Decoding

public class AsciiEncodingDecoding {

    public static void main(String[] args) {
        
        String message = "Hello, World!";
        String encodedMessage = encodeAscii(message);
        String decodedMessage = decodeAscii(encodedMessage);
        
        System.out.println("Encoded message: " + encodedMessage);
        System.out.println("Decoded message: " + decodedMessage);
    }
    
    public static String encodeAscii(String message) {
        
        StringBuilder encodedMessage = new StringBuilder();
        
        for (int i = 0; i < message.length(); i++) {
            int asciiValue = (int) message.charAt(i);
            encodedMessage.append(asciiValue);
            if (i != message.length() - 1) {
                encodedMessage.append(" ");
            }
        }
        
        return encodedMessage.toString();
    }
    
    public static String decodeAscii(String encodedMessage) {
        
        String[] asciiValues = encodedMessage.split(" ");
        StringBuilder decodedMessage = new StringBuilder();
        
        for (String asciiValue : asciiValues) {
            int intValue = Integer.parseInt(asciiValue);
            char decodedChar = (char) intValue;
            decodedMessage.append(decodedChar);
        }
        
        return decodedMessage.toString();
    }
}

In this example We define two methods in this example, encodeAscii and decodeAscii, to handle the encoding and decoding of the message using ASCII. A string representation of the encoded message is returned by the encodeAscii method after converting each character in the input string message to its corresponding ASCII value. Decoding each ASCII value back into its corresponding character using the decodeAscii method results in a string representation of the decoded message.

In the main method, the message "Hello, World!" is encoded using the encodeAscii method.The decodeAscii method is then used to decode the message, and the outcomes are printed to the console.

There are numerous other libraries that can be used for data encoding and decoding in Java; this is just one example of how encoding and decoding can be implemented in Java.

Encoded message: 72 101 108 108 111 44 32 87 111 114 108 100 33
Decoded message: Hello, World! 

URL Encoding and Decoding

Java's Base64 class also supports URL-safe encoding and decoding, which replaces the '+' and '/' characters with '-' and '_' characters respectively. This is useful for encoding data that will be included in URLs or other web-related contexts.

To perform URL-safe encoding and decoding, you can use the following methods

Base64.getUrlEncoder().encodeToString(byte[] bytes) :

This method encodes a byte array into a URL-safe Base64-encoded string

Base64.getUrlDecoder().decode(String base64) :

This method decodes a URL-safe Base64-encoded string into a byte array

Java Example of Basic Encoding and Decoding

import java.util.Base64;

public class Base64Example {

public static void main(String[] args) {
    
    // Encode a string using URL-safe encoding
    String originalString = "https://www.dockertpoint.com/what-is-java.php;
    String encodedString = Base64.getUrlEncoder().encodeToString(originalString.getBytes());
    System.out.println("Encoded string: " + encodedString);
    
    // Decode a URL-safe encoded string
    byte[] decodedBytes = Base64.getUrlDecoder().decode(encodedString);
    String decodedString = new String(decodedBytes);
    System.out.println("Decoded string: " + decodedString);
    
}

}

In this example, we first create a String object containing a URL. We then use the getBytes() method to convert this string into a byte array. Next, we encode the byte array using the Base64.getUrlEncoder().encodeToString() method and store the result in a new string called encodedString. We then print out the encoded string.

In the second part of the example, we decode the encoded string using the Base64.getUrlDecoder().decode() method. This method returns a byte array, which we then convert back into a string using the new String() constructor. Finally, we print out the decoded string.

As you can see, the encoded string is URL-safe and can be included in a URL without causing any issues.

Encoded string: aHR0cHM6Ly93d3cuZXhhbXBsZS5jb20vcGF0aC90by9yZXNvdXJjZT9wYXJhbT12YWx1ZQ==
Decoded string: https://www.dockertpoint.com/what-is-java.php
 

MIME Encoding and Decoding

Java's Base64 class also supports MIME encoding and decoding, which adds line breaks after every 76 characters and uses the characters '+' and '/' for encoding. This is useful for encoding data for email transmission, as MIME-encoded messages often have line length restrictions.

To perform MIME encoding and decoding, you can use the following methods

Base64.getMimeEncoder().encodeToString(byte[] bytes) :

This method encodes a byte array into a MIME Base64-encoded string

Base64.getMimeDecoder().decode(String base64) :

This method decodes a MIME Base64-encoded string into a byte array

Java Example of Basic Encoding and Decoding

import java.util.Base64;

public class Base64Example {

public static void main(String[] args) {
    
    // Encode a string using MIME encoding
    String originalString = "This is a long string that needs to be MIME-encoded to be transmitted via email";
    String encodedString = Base64.getMimeEncoder().encodeToString(originalString.getBytes());
    System.out.println("Encoded string: " + encodedString);
    
    // Decode a MIME-encoded string
    byte[] decodedBytes = Base64.getMimeDecoder().decode(encodedString);
    String decodedString = new String(decodedBytes);
    System.out.println("Decoded string: " + decodedString);
    
}

}

In this example, we first create a String object containing a long message. We then use the getBytes() method to convert this string into a byte array. Next, we encode the byte array using the Base64.getMimeEncoder().encodeToString() method and store the result in a new string called encodedString. We then print out the encoded string.

In the second part of the example, we decode the encoded string using the Base64.getMimeDecoder().decode() method. This method returns a byte array, which we then convert back into a string using the new String() constructor. Finally, we print out the decoded string.

As you can see, the encoded string has line breaks after every 76 characters, as specified by the MIME standard.

Encoded string: VGhpcyBpcyBhIGxvbmcgc3RyaW5nIHRoYXQgbmVlZHMgdG8gYmUgTUlNRS1lbmNvZGVkIHR
vIGJlIHRyYW5zbWl0ZWQgdmlhIGVtYWlsICAgCnZpYSBlbmNvZGVkIHRvIHJlc3BvbnNlIHZpYQ==

Decoded string: This is a long string that needs to be MIME-encoded to be transmitted via email