code: public boolean learn(String... wordTags)
      {
          String[] words = new String[wordTags.length];
          String[] tags = new String[wordTags.length];
          for (int i = 0; i < wordTags.length; i++)
          {
              String[] wordTag = wordTags[i].split("//");
              words[i] = wordTag[0];
              tags[i] = wordTag[1];
          }
          return learn(new POSInstance(words, tags, model.featureMap));
      }
docs: 在线学习
  
  @param wordTags [单词]/[词性]数组
  @return 是否学习成功（失败的原因是参数错误）