How Gson serializes a byte array

GsonTest.java

import com.google.gson.Gson;
import java.security.MessageDigest;

public class GsonTest {
    private final byte[] sha1;

    public GsonTest(byte[] sha1) {
        this.sha1 = sha1;
    }

    public static void main(String[] args) throws Exception {
        MessageDigest md = MessageDigest.getInstance("SHA1");
        GsonTest gt = new GsonTest(md.digest());
        System.out.println(new Gson().toJson(gt));
        // Prints: {"sha1":[-38,57,-93,-18,94,107,75,13,50,85,-65,-17,-107,96,24,-112,-81,-40,7,9]}
    }
}