Base64 Encoding in Java

Java provides built-in support for base64 encoding/decoding.

import java.util.Base64;

public class Base64Encoding {
    public static void main(String[] args) {
        // Here's the string we'll encode/decode.
        String data = "abc123!?$*&()'-=@~";

        // Java supports both standard and URL-compatible
        // base64. Here's how to encode using the standard
        // encoder. The encoder requires a byte array, so we
        // convert our string to that type.
        String sEnc = Base64.getEncoder().encodeToString(data.getBytes());
        System.out.println(sEnc);

        // Decoding may throw an exception, which you can catch
        // if you don't already know the input to be
        // well-formed.
        try {
            byte[] sDec = Base64.getDecoder().decode(sEnc);
            System.out.println(new String(sDec));
        } catch (IllegalArgumentException e) {
            System.out.println("Decoding failed: " + e.getMessage());
        }
        System.out.println();

        // This encodes/decodes using a URL-compatible base64
        // format.
        String uEnc = Base64.getUrlEncoder().encodeToString(data.getBytes());
        System.out.println(uEnc);
        try {
            byte[] uDec = Base64.getUrlDecoder().decode(uEnc);
            System.out.println(new String(uDec));
        } catch (IllegalArgumentException e) {
            System.out.println("Decoding failed: " + e.getMessage());
        }
    }
}

The string encodes to slightly different values with the standard and URL base64 encoders (trailing + vs -) but they both decode to the original string as desired.

$ java Base64Encoding
YWJjMTIzIT8kKiYoKSctPUB+
abc123!?$*&()'-=@~

YWJjMTIzIT8kKiYoKSctPUB-
abc123!?$*&()'-=@~

In Java, we use the java.util.Base64 class for base64 encoding and decoding. The Base64.getEncoder() and Base64.getDecoder() methods provide standard base64 encoding and decoding, while Base64.getUrlEncoder() and Base64.getUrlDecoder() provide URL-safe encoding and decoding.

The encodeToString() method is used for encoding, which takes a byte array as input. To decode, we use the decode() method, which returns a byte array. We then convert this byte array back to a string for printing.

Note that in Java, decoding can throw an IllegalArgumentException if the input is not properly formatted base64. It’s good practice to catch this exception when decoding.

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Base64 Encoding in Java