需要导入：

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

/**
 * 图片转base64字符串
 * @param path
 * @return
 */
public static String PictoBase64(String path) {
  InputStream in = null;
  byte[] data = null;
  // 读取图片字节数组
  try {
    in = new FileInputStream(path);
    data = new byte[in.available()];
    in.read(data);
    in.close();
  } catch (IOException e) {
    e.printStackTrace();
  }
  // 对字节数组Base64编码
  BASE64Encoder encoder = new BASE64Encoder();
  return encoder.encode(data);// 返回Base64编码过的字节数组字符串
}

/**
 * base64写图片
 * @param imgStr
 * @return
 */
public static boolean Base64toPic(String imgStr) {

  // 对字节数组字符串进行Base64解码并生成图片
  if (imgStr == null) // 图像数据为空
    return false;
  BASE64Decoder decoder = new BASE64Decoder();
  try {
    // Base64解码
    byte[] b = decoder.decodeBuffer(imgStr);
    for (int i = 0; i < b.length; ++i) {
      if (b[i] < 0) {// 调整异常数据
        b[i] += 256;
      }
    }
    String imgName = UUID.randomUUID().toString().replace("-", "");
    String imgType = ".png";
    // 生成png图片
    String imgFilePath = "C:/Users/Administrator/Desktop/" + imgName + imgType;// 新生成的图片
    OutputStream out = new FileOutputStream(imgFilePath);
    out.write(b);
    out.flush();
    out.close();
    return true;
  } catch (Exception e) {
    return false;
  }
}