176

Okay, I know how to do it in C#.

It's as simple as:

Convert.ToBase64String(byte[])
and Convert.FromBase64String(string) to get byte[] back.

How can I do this in Java?

Sorantis
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4 Answers4

317

Java 8+

Encode or decode byte arrays:

byte[] encoded = Base64.getEncoder().encode("Hello".getBytes());
println(new String(encoded));   // Outputs "SGVsbG8="

byte[] decoded = Base64.getDecoder().decode(encoded);
println(new String(decoded))    // Outputs "Hello"

Or if you just want the strings:

String encoded = Base64.getEncoder().encodeToString("Hello".getBytes());
println(encoded);   // Outputs "SGVsbG8="

String decoded = new String(Base64.getDecoder().decode(encoded.getBytes()));
println(decoded)    // Outputs "Hello"

For more info, see Base64.

Java < 8

Base64 is not bundled with Java versions less than 8. I recommend using Apache Commons Codec.

For direct byte arrays:

Base64 codec = new Base64();
byte[] encoded = codec.encode("Hello".getBytes());
println(new String(encoded));   // Outputs "SGVsbG8="

byte[] decoded = codec.decode(encoded);
println(new String(decoded))    // Outputs "Hello"

Or if you just want the strings:

Base64 codec = new Base64();
String encoded = codec.encodeBase64String("Hello".getBytes());
println(encoded);   // Outputs "SGVsbG8="

String decoded = new String(codec.decodeBase64(encoded));
println(decoded)    // Outputs "Hello"

Spring

If you're working in a Spring project already, you may find their org.springframework.util.Base64Utils class more ergonomic:

For direct byte arrays:

byte[] encoded = Base64Utils.encode("Hello".getBytes());
println(new String(encoded))    // Outputs "SGVsbG8="

byte[] decoded = Base64Utils.decode(encoded);
println(new String(decoded))    // Outputs "Hello"

Or if you just want the strings:

String encoded = Base64Utils.encodeToString("Hello".getBytes());
println(encoded);   // Outputs "SGVsbG8="

String decoded = Base64Utils.decodeFromString(encoded);
println(new String(decoded))    // Outputs "Hello"

Android (with Java < 8)

If you are using the Android SDK before Java 8 then your best option is to use the bundled android.util.Base64.

For direct byte arrays:

byte[] encoded = Base64.encode("Hello".getBytes());
println(new String(encoded))    // Outputs "SGVsbG8="

byte [] decoded = Base64.decode(encoded);
println(new String(decoded))    // Outputs "Hello"

Or if you just want the strings:

String encoded = Base64.encodeToString("Hello".getBytes());
println(encoded);   // Outputs "SGVsbG8="

String decoded = new String(Base64.decode(encoded));
println(decoded)    // Outputs "Hello"
Cory Klein
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    On Android, the `encode` and `encodeToString` methods also expect a `flags` parameter, so you need to do `Base64.encode("Hello".getBytes(), Base64.DEFAULT);` (and the same for `encodeToString`). – Donald Duck Aug 10 '21 at 09:58
33

Use:

byte[] data = Base64.encode(base64str);

Encoding converts to Base64

You would need to reference commons codec from your project in order for that code to work.

For java8:

import java.util.Base64
F.O.O
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Konstantin Spirin
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    The methods for encode / decode of class Base64 are static so you don't need to create a new object. Then: byte [] data = Base64.decode(base64str); is enough. – Ernesto Campohermoso Nov 08 '13 at 15:25
18

Additionally, for our Android friends (API Level 8):

import android.util.Base64

...

Base64.encodeToString(bytes, Base64.DEFAULT);
Ton Snoei
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8

In case you happen to be using Spring framework along with java, there is an easy way around.

  1. Import the following.

    import org.springframework.util.Base64Utils;

  2. Convert like this.

    byte[] bytearr ={0,1,2,3,4};
String encodedText = Base64Utils.encodeToString(bytearr);

    To decode you can use the decodeToString method of the Base64Utils class.

Ihsan Izwer
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