code: public void append(byte[] data) {
          if (data.length >= (this.datas.length - size)) {
              // 扩容
              byte[] newData = new byte[this.datas.length + data.length + this.datas.length / 2];
              System.arraycopy(this.datas, 0, newData, 0, size);
              this.datas = newData;
          }
          System.arraycopy(data, 0, this.datas, size, data.length);
          this.size += data.length;
          modCount++;
      }
docs: 向byte数组中添加数据
  
  @param data
  添加的数据，不能为null