code: public PropertiesProxy joinAndClose(Reader r) {
          MultiLineProperties mp = new MultiLineProperties();
          try {
              mp.load(r);
          }
          catch (IOException e) {
              throw Lang.wrapThrow(e);
          }
          finally {
              Streams.safeClose(r);
          }
          this.putAll(mp);
          return this;
      }
docs: 将另外一个 Properties 文本加入本散列表
  
  @param r
  文本输入流
  @return 自身