package Base64ToArray;
import java.io.*;
import java.util.Base64;
public class Base64ToFile {
    public static void main(String[] args) {
        String filePath = "D:/1.png";
        String base64 = fileToBase64(filePath);
        System.out.println(base64);
        base64StringToFile(base64, "D:", "sexy.png");
    }
    /**
     * Convert a file to a base64 string
     *
     * @param filePath
     * @return
     */
    public static String fileToBase64(String filePath) {
        if (filePath == null)
            return null;
        byte[] data = null;
        try {
            InputStream in = new FileInputStream(filePath);
            data = new byte[in.available()];
            in.read(data);
            in.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        String encodedString = Base64.getEncoder().encodeToString(data);
        return encodedString;
    }
    /**
     * convert a base64 string to a file
     *
     * @param encodedString
     * @param filePath
     * @param fileName
     * @return
     */
    public static boolean base64StringToFile(String encodedString, String filePath, String fileName) {
        if (encodedString == null || filePath == null || fileName == null)
            return false;
        byte[] data = Base64.getDecoder().decode(encodedString);
        try {
            OutputStream out = new FileOutputStream(filePath + File.separator + fileName);
            out.write(data);
            out.flush();
            out.close();
            return true;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return false;
    }
}

参考

• byte数组，图片，base64互相转换——CSDN