OKHttp 3如何设置post请求编码？我用了RequestBody.create方法

这是create的源码：

public static RequestBody create(MediaType contentType, String content) {
    Charset charset = Util.UTF_8;
    if (contentType != null) {
      charset = contentType.charset();
      if (charset == null) {
        charset = Util.UTF_8;
        contentType = MediaType.parse(contentType + "; charset=utf-8");
      }
    }
    byte[] bytes = content.getBytes(charset);
    return create(contentType, bytes);
  }

这个content是post的话是类似“a=88&b=99”这样的字符串吗？
测试了好几次了。。

---

private final OkHttpClient client = new OkHttpClient();

public void run() throws Exception {

RequestBody formBody = new FormBody.Builder()
    .add("search", "Jurassic Park")
    .build();
Request request = new Request.Builder()
    .url("https://en.wikipedia.org/w/index.php")
    .post(formBody)
    .build();

Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

System.out.println(response.body().string());

}