Java Word PDF PPT 读写

把变成字符流,再写到另外一个文件,怎么就打不开了?要怎样操作的呢?一定要POI之类的吗?                String filePath="C:\\Java-Exception.ppt";
                File distFile = new File(filePath); 
                String contect=FileMaster.file2String(distFile,"gbk");
String contect1=encode(contect,"gbk");//加密
String contect2=decode(contect1,"gbk"); //解密
String filePathAndName="C:\\base64Java-Exception.ppt";
                FileMaster.newFile(filePathAndName, contect2);