Base64.Decoder

AI-generated Key Takeaways

• Base64.Decoder is a class for decoding byte data using the Base64 encoding scheme, as defined in RFC 4648 and RFC 2045.

• It handles Base64 padding characters ('=') but does not require them for decoding.

• The decoder is thread-safe and throws IllegalArgumentException if the input is not in a valid Base64 format.

• It provides various methods for decoding Base64 encoded data from different sources like strings, byte arrays, and ByteBuffers.

• An InputStream can be wrapped using wrap() for decoding Base64 encoded streams.

public static class Base64.Decoder extends Object

This class implements a decoder for decoding byte data using the Base64 encoding scheme as specified in RFC 4648 and RFC 2045.

The Base64 padding character '=' is accepted and interpreted as the end of the encoded byte data, but is not required. So if the final unit of the encoded byte data only has two or three Base64 characters (without the corresponding padding character(s) padded), they are decoded as if followed by padding character(s). If there is a padding character present in the final unit, the correct number of padding character(s) must be present, otherwise IllegalArgumentException ( IOException when reading from a Base64 stream) is thrown during decoding.

Instances of Base64.Decoder class are safe for use by multiple concurrent threads.

Unless otherwise noted, passing a null argument to a method of this class will cause a NullPointerException to be thrown.

See Also

• Base64.Encoder

Public Method Summary

byte[]	decode(String src) Decodes a Base64 encoded String into a newly-allocated byte array using the Base64 encoding scheme.
int	decode(byte[] src, byte[] dst) Decodes all bytes from the input byte array using the Base64 encoding scheme, writing the results into the given output byte array, starting at offset 0.
byte[]	decode(byte[] src) Decodes all bytes from the input byte array using the Base64 encoding scheme, writing the results into a newly-allocated output byte array.
ByteBuffer	decode(ByteBuffer buffer) Decodes all bytes from the input byte buffer using the Base64 encoding scheme, writing the results into a newly-allocated ByteBuffer.
InputStream	wrap(InputStream is) Returns an input stream for decoding Base64 encoded byte stream.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Public Methods

public byte[] decode (String src)

Decodes a Base64 encoded String into a newly-allocated byte array using the Base64 encoding scheme.

An invocation of this method has exactly the same effect as invoking decode(src.getBytes(StandardCharsets.ISO_8859_1))

Parameters

src	the string to decode

Returns

• A newly-allocated byte array containing the decoded bytes.

Throws

IllegalArgumentException	if src is not in valid Base64 scheme

public int decode (byte[] src, byte[] dst)

Decodes all bytes from the input byte array using the Base64 encoding scheme, writing the results into the given output byte array, starting at offset 0.

It is the responsibility of the invoker of this method to make sure the output byte array dst has enough space for decoding all bytes from the input byte array. No bytes will be be written to the output byte array if the output byte array is not big enough.

If the input byte array is not in valid Base64 encoding scheme then some bytes may have been written to the output byte array before IllegalargumentException is thrown.

Parameters

src	the byte array to decode
dst	the output byte array

Returns

• The number of bytes written to the output byte array

Throws

IllegalArgumentException	if src is not in valid Base64 scheme, or dst does not have enough space for decoding all input bytes.

public byte[] decode (byte[] src)

Decodes all bytes from the input byte array using the Base64 encoding scheme, writing the results into a newly-allocated output byte array. The returned byte array is of the length of the resulting bytes.

Parameters

src	the byte array to decode

Returns

• A newly-allocated byte array containing the decoded bytes.

Throws

IllegalArgumentException	if src is not in valid Base64 scheme

public ByteBuffer decode (ByteBuffer buffer)

Decodes all bytes from the input byte buffer using the Base64 encoding scheme, writing the results into a newly-allocated ByteBuffer.

Upon return, the source buffer's position will be updated to its limit; its limit will not have been changed. The returned output buffer's position will be zero and its limit will be the number of resulting decoded bytes

IllegalArgumentException is thrown if the input buffer is not in valid Base64 encoding scheme. The position of the input buffer will not be advanced in this case.

Parameters

buffer	the ByteBuffer to decode

Returns

• A newly-allocated byte buffer containing the decoded bytes

Throws

IllegalArgumentException	if src is not in valid Base64 scheme.

public InputStream wrap (InputStream is)

Returns an input stream for decoding Base64 encoded byte stream.

The read methods of the returned InputStream will throw IOException when reading bytes that cannot be decoded.

Closing the returned input stream will close the underlying input stream.

Parameters

is	the input stream

Returns

• the input stream for decoding the specified Base64 encoded byte stream