Java Base64 Encode and Decode

21 Apr 2025 | 5 min read

Java provides a class Base64 to deal with encryption. You can encrypt and decrypt your data by using provided methods. You need to import java.util.Base64 in your source file to use its methods.

This class provides three different encoders and decoders to encrypt information at each level. You can use these methods at the following levels.

Basic Encoding and Decoding

It uses the Base64 alphabet specified by Java in RFC 4648 and RFC 2045 for encoding and decoding operations. The encoder does not add any line separator character. The decoder rejects data that contains characters outside the base64 alphabet.

URL and Filename Encoding and Decoding

It uses the Base64 alphabet specified by Java in RFC 4648 for encoding and decoding operations. The encoder does not add any line separator character. The decoder rejects data that contains characters outside the base64 alphabet.

MIME

It uses the Base64 alphabet as specified in RFC 2045 for encoding and decoding operations. The encoded output must be represented in lines of no more than 76 characters each and uses a carriage return '\r' followed immediately by a linefeed '\n' as the line separator. No line separator is added to the end of the encoded output. All line separators or other characters not found in the base64 alphabet table are ignored in decoding operation.

Nested Classes of Base64

Class	Description
Base64.Decoder	This class implements a decoder for decoding byte data using the Base64 encoding scheme as specified in RFC 4648 and RFC 2045.
Base64.Encoder	This class implements an encoder for encoding byte data using the Base64 encoding scheme as specified in RFC 4648 and RFC 2045.

Base64 Methods

Methods	Description
public static Base64.Decoder getDecoder()	It returns a Base64.Decoder that decodes using the Basic type base64 encoding scheme.
public static Base64.Encoder getEncoder()	It returns a Base64.Encoder that encodes using the Basic type base64 encoding scheme.
public static Base64.Decoder getUrlDecoder()	It returns a Base64.Decoder that decodes using the URL and Filename safe type base64 encoding scheme.
public static Base64.Decoder getMimeDecoder()	It returns a Base64.Decoder that decodes using the MIME type base64 decoding scheme.
public static Base64.Encoder getMimeEncoder()	It Returns a Base64.Encoder that encodes using the MIME type base64 encoding scheme.
public static Base64.Encoder getMimeEncoder(int lineLength, byte[] lineSeparator)	It returns a Base64.Encoder that encodes using the MIME type base64 encoding scheme with specified line length and line separators.
public static Base64.Encoder getUrlEncoder()	It returns a Base64.Encoder that encodes using the URL and Filename safe type base64 encoding scheme.

Base64.Decoder Methods

Methods	Description
public byte[] decode(byte[] src)	It 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.
public byte[] decode(String src)	It decodes a Base64 encoded String into a newly-allocated byte array using the Base64 encoding scheme.
public int decode(byte[] src, byte[] dst)	It 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.
public ByteBuffer decode(ByteBuffer buffer)	It decodes all bytes from the input byte buffer using the Base64 encoding scheme, writing the results into a newly-allocated ByteBuffer.
public InputStream wrap(InputStream is)	It returns an input stream for decoding Base64 encoded byte stream.

Base64.Encoder Methods

Methods	Description
public byte[] encode(byte[] src)	It encodes all bytes from the specified byte array into a newly-allocated byte array using the Base64 encoding scheme. The returned byte array is of the length of the resulting bytes.
public int encode(byte[] src, byte[] dst)	It encodes all bytes from the specified byte array using the Base64 encoding scheme, writing the resulting bytes to the given output byte array, starting at offset 0.
public String encodeToString(byte[] src)	It encodes the specified byte array into a String using the Base64 encoding scheme.
public ByteBuffer encode(ByteBuffer buffer)	It encodes all remaining bytes from the specified byte buffer into a newly-allocated ByteBuffer using the Base64 encoding scheme. 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 encoded bytes.
public OutputStream wrap(OutputStream os)	It wraps an output stream for encoding byte data using the Base64 encoding scheme.
public Base64.Encoder withoutPadding()	It returns an encoder instance that encodes equivalently to this one, but without adding any padding character at the end of the encoded byte data.

Java Base64 Example: Basic Encoding and Decoding

Output:

 Encoded byte array: [B@6bc7c054 Encoded byte array written to another array: [B@232204a1 Number of bytes written: 4 Encoded string: SmF2YVRwb2ludA== Decoded string: JavaTpoint

Java Base64 Example: URL Encoding and Decoding

Output:

 Encoded URL: aHR0cDovL3d3dy5qYXZhdHBvaW50LmNvbS9qYXZhLXR1dG9yaWFsLw== Decoded URL: http://www.javatpoint.com/java-tutorial/

Java Base64 Example: MIME Encoding and Decoding

Output:

 Encoded MIME message: SGVsbG8sIApZb3UgYXJlIGluZm9ybWVkIHJlZ2FyZGluZyB5b3VyIGluY29uc2lzdGVuY3kgb2Yg d29yaw== Decoded message: Hello, You are informed regarding your inconsistency of work

Next TopicJava Default Methods

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Java Base64 Encode and Decode

Basic Encoding and Decoding

URL and Filename Encoding and Decoding

MIME

Nested Classes of Base64

Base64 Methods

Base64.Decoder Methods

Base64.Encoder Methods

Java Base64 Example: Basic Encoding and Decoding

Java Base64 Example: URL Encoding and Decoding

Java Base64 Example: MIME Encoding and Decoding

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Java Base64 Encode and Decode

Basic Encoding and Decoding

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Java Base64 Example: Basic Encoding and Decoding

Java Base64 Example: URL Encoding and Decoding

Java Base64 Example: MIME Encoding and Decoding

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