Java Base64 Decode

In Java Base64 Decode, Base64 is an encoding scheme in a binary-to-text format that denotes binary data, which is in the form of printable ASCII string format by translating into radix 64 depictions. These Base64 data can be encoded or decoded based on the user’s requirements and can be done with the help of certain methods. For that, importing java.util.Base64 package is an essential step. The main advantage of encoding and decoding these data is its privacy as well as security. In the following sections, a detailed description of each method will be addressed.

Start Your Free Software Development Course

Web development, programming languages, Software testing & others

Declaration:

Below is the declaration for Base64 decode:

public static class Base64.Decoder extends Object

How does Base64 Decode Work in Java?

Now,  let us see the working of the Base64 decode.

• First, create an encoder object and encode the string/ bytes/ bytebuffer based on the requirement. It can be done using the method Base64.getEncoder().
• Once it is done, create a new array for the encoded data.
• To decode the data, create a decoder object, and create another array for storing decoded data.
• Decode the encoded data using the method decode().
• Print the result available in the decoder array.

Methods of Java Base64 decode

Following are the different methods of Java Base64 decode.

1. public byte[] decode ( byte[] arr )

• Decodes each and every byte from the input array with the help of the Base64 encoding scheme.
• Results will be written into a newly allocated byte array.
• The byte array returned will be having a length similar to the resulting bytes.
• Here, arr is the input byte array that has to be decoded.
• An IllegalArgumentException will be thrown if the input byte array is not in a valid format of Base64.

Example:

Code:

import java.util.Base64;
public class Base64DecodeExample {
public static void main(String[] args) {
//  encoder
Base64.Encoder enc = Base64.getEncoder();
// Encode byte array
byte arr[] = {'a'};
byte arr2[] = enc.encode(arr);
System.out.println("Array encoded is: "+ arr2);
//  decoder
Base64.Decoder dec = Base64.getDecoder();
// Decode byte array
String ds = new String(dec.decode(arr2));
System.out.println("Array decoded is:"+ds);
}
}

Output:

An encoded and decoded result of an array gets printed on executing the code.

2. public byte[] decode ( Stringstr )

• Input string which is in the Base64 format, will be decoded with the help of the Base64 encoding scheme.
• Results will be written into a newly allocated byte array.
• Execution of this method will create an effect of executing the method decode( src.getBytes ( StandardCharsets.ISO_8859_1 ) ).
• Here, str is the input string that has to be decoded.
• An IllegalArgumentException will be thrown if the input string is not in a valid format of Base64.

Example:

Code:

import java.util.Base64;
public class Base64DecodeExample {
public static void main(String[] args) {
//  encoder
Base64.Encoder enc = Base64.getEncoder();
String s = enc.encodeToString("EduCBA".getBytes());
System.out.println("String encoded is: "+ s);
//  decoder
Base64.Decoder dec = Base64.getDecoder();
// Decode string
String ds = new String(dec.decode(s));
System.out.println("String decoded is:"+ds);
}}

Output:

An encoded and decoded result of a string gets printed on executing the code.

3. public int decode ( byte[] arr, byte[] arr2)

• Decodes each and every byte from the input array with the help of the Base64 encoding scheme.
• Results will be written into a byte array arr2 that starts the offset from 0.
• Here, arr is the input byte array that has to be decoded, and arr2 is the output array. Make sure that arr2 has enough space to accommodate the decoded input bytes.
• An IllegalArgumentException will be thrown if the input byte array is not in a valid format of Base64 or arr2 do not have enough space for writing the decoded input bytes.

Example:

Code:

import java.util.Base64;
public class Base64DecodeExample {
public static void main(String[] args) {
//  encoder
Base64.Encoder enc = Base64.getEncoder();
byte arr[] = {'1'};
byte arr2[] = enc.encode(arr);
byte arr3[] = new byte[5];
System.out.println("Array encoded is: "+ arr2);
//  decoder
Base64.Decoder dec = Base64.getDecoder();
System.out.println("Array decoded is:"+ dec.decode(arr2,arr3));
}}

Output:

An encoded and decoded result of a byte array gets printed on executing the code.

4. public ByteBufferdecode ( ByteBufferbuff )

• Decodes each and every byte from the input byte buffer with the help of the Base64 encoding scheme.
• Results will be written into a newly allocated bytebuffer.
• Here, the buff is the inputbytebuffer that has to be decoded.
• An IllegalArgumentException will be thrown if the input bytebufferis not in a valid format of Base64.

Example:

Code:

import java.nio.ByteBuffer;
import java.util.Base64;
public class Base64DecodeExample {
public static void main(String[] args) {
//  encoder
Base64.Encoder enc = Base64.getEncoder();
String st = "Happy weekend";
ByteBuffer buff= ByteBuffer.wrap(st.getBytes());
ByteBuffer buff2 = enc.encode(buff);
System.out.print("Encoded: ");
while(buff2.hasRemaining()){
char ch = (char) buff2.get();
System.out.print(ch);
}
buff2.clear();
//  decoder
Base64.Decoder dec = Base64.getDecoder();
ByteBuffer buff3 = dec.decode(buff2);
System.out.print(" Decoded: ");
while(buff3.hasRemaining()){
char ch3 = (char) buff3.get();
System.out.print(ch3);
}
buff2.clear();
}
}

Output:

An encoded and decoded result of a bytebuffergets printed on executing the code.

5. public InputStreamwrap ( InputStreaminpt )

• An input stream will be returned in order to decode the byte stream, which is Base64 encoded.
• Here, input is the input stream.

Example

Code:

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Base64;
public class Base64DecodeExample {
public static void main(String[] args) throws IOException {
try (InputStream inpt       = new FileInputStream("F:\\EduCBA\\April\\Edu.txt"))
{
Base64.Encoder enc = Base64.getEncoder();
OutputStream opst = enc.wrap(new FileOutputStream("F:\\EduCBA\\April\\Eduout.txt"));
int b1;
while ((b1 = inpt.read()) != -1)
{
opst.write(b1);
}
opst.close();
}
catch (IOException ie)
{
System.err.printf("I/O exception", ie.getMessage());
}
try (FileOutputStream fopst = new FileOutputStream("F:\\EduCBA\\April\\Eduou.txt"))
{
Base64.Decoder dec = Base64.getDecoder();
InputStream inpt2 = dec.wrap(new FileInputStream("F:\\EduCBA\\April\\Eduout.txt"));
int b1;
while ((b1 = inpt2.read()) != -1)
fopst.write(b1);
inpt2.close();
}
catch (IOException ie)
{
System.err.printf("I/O exception", ie.getMessage());
}
}
}

Output:

In this program, create three create text files, Edu, Eduout, Eduou, in a location for storing data, encoded data, and decoded data respectively. The below figure is the input data.

The encoded and decoded data will be written into the two other files on executing the code, as shown below.

The above is the detailed content of Java Base64 Decode. For more information, please follow other related articles on the PHP Chinese website!