Essential Books

Base64 Encoding Decoding

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Occasionally you will find the need to encode binary data as a base64-encoded string.

For this we can use the DatatypeConverter class from the javax.xml.bind package: 

import javax.xml.bind.DatatypeConverter;
import java.util.Arrays;

// arbitrary binary data specified as a byte array
byte[] binaryData = "some arbitrary data".getBytes("UTF-8");

// convert the binary data to the base64-encoded string
String encodedData = DatatypeConverter.printBase64Binary(binaryData);
// encodedData is now "c29tZSBhcmJpdHJhcnkgZGF0YQ=="

// convert the base64-encoded string back to a byte array
byte[] decodedData = DatatypeConverter.parseBase64Binary(encodedData);

// assert that the original data and the decoded data are equal
assert Arrays.equals(binaryData, decodedData);

Apache commons-codec

Alternatively, we can use Base64 from Apache commons-codec. 

import org.apache.commons.codec.binary.Base64;

// your blob of binary as a byte array
byte[] blob = "someBinaryData".getBytes();

// use the Base64 class to encode
String binaryAsAString = Base64.encodeBase64String(blob);

// use the Base64 class to decode
byte[] blob2 = Base64.decodeBase64(binaryAsAString);

// assert that the two blobs are equal
System.out.println("Equal : " + Boolean.toString(Arrays.equals(blob, blob2)));

If you inspect this program wile running, you will see that someBinaryData encodes to c29tZUJpbmFyeURhdGE=, a very managable UTF-8 String object.

—

Details for the same can be found at Base64 

// encode with padding
String encoded = Base64.getEncoder().encodeToString(someByteArray);

// encode without padding
String encoded = Base64.getEncoder().withoutPadding().encodeToString(someByteArray);

// decode a String
byte [] barr = Base64.getDecoder().decode(encoded);

Reference

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Converting to and from strings:
* Converting to and from Strings
* Converting String to other datatypes.
* Conversion to from bytes
* Base64 Encoding Decoding
* Converting other datatypes to String
* Getting a String from an InputStream
* Parsing Strings to a Numerical Value
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