提供公共API来获取当前输入字母的最有可能单词候选项和当前句子的最有可能单词。

可以使用Google的输入法API来实现这个功能。API将返回包含当前句子和当前输入字母所期望的单词候选项的数据列表。以下是使用Java语言调用API的示例代码：

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import org.json.JSONArray;

public class WordSuggestion {
  public static void main(String[] args) throws Exception {
    String input = "th";
    String sentence = "I am writing a sentence.";
    JSONArray suggestions = getSuggestions(input, sentence);
    System.out.println(suggestions);
  }

  public static JSONArray getSuggestions(String input, String sentence) throws Exception {
    String urlStr =
        "https://inputtools.google.com/request?"
            + "text="
            + URLEncoder.encode(sentence, "UTF-8")
            + "&itc="
            + URLEncoder.encode("en-t-i0-und", "UTF-8")
            + "&num=10&cp=0&cs=1&ie=utf-8&oe=utf-8&app=test";
    URL url = new URL(urlStr);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("GET");
    conn.setRequestProperty("User-Agent", "Mozilla/5.0");
    InputStream is = conn.getInputStream();
    BufferedReader rd = new BufferedReader(new InputStreamReader(is));
    String line;
    StringBuffer response = new StringBuffer();
    while ((line = rd.readLine()) != null) {
      response.append(line);
      response.append('\r');
    }
    rd.close();
    JSONArray jsonArray = new JSONArray(response.toString());
    JSONArray resultArr = jsonArray.getJSONArray(1);
    JSONArray suggestionsArr = new JSONArray();
    for (int i = 0; i < resultArr.length(); i++) {
      JSONArray arr = resultArr.getJSONArray(i);
      if (arr.length() > 2 && arr.getString(1).equals(input)) {
        JSONArray suggArr = arr.getJSONArray(2);
        for (int j = 0; j < suggArr.length(); j++) {
          suggestionsArr.put(suggArr.getString(j));
        }
      }
    }
    return suggestionsArr;
  }
}