Java calling external program blocking code with runtime

Sometimes external programs are called in Java code, such as Swftools to convert SWF, ffmpeg to convert video, and so on. If your code writes like this: Runtime.getruntime (). EXEC (command), you will find that the program is executed, and at the command line to perform a bit, because Java does not wait for the external program to complete, it is necessary to use blocking, To wait for external program execution results:

InputStream stderr =new InputStreamReader (stderr, "GBK"newnull ;  while NULL )    System.out.println (line); int exitvalue = process.waitfor ();

For a general external program to use the above blocking code, at least Pdf2swf.exe is no problem.

But I found that for ffmpeg, the above code will make the program stuck, need to use another way, encapsulated into a method, as follows:

　　　　 @SuppressWarnings ("static-access") public static int dowaitfor (process process) {InputStream in = Null;inputstream err = Null;int Exitvalue =-1;  Returned to caller when P was finishedtry {in = Process.getinputstream (); err = Process.geterrorstream (); Boolean finished = false; Set to True when P was Finishedwhile (!finished) {try {while (in.available () > 0) {//Print the output of our system Callcharacter C = new Character ((char) in.read ()); System.out.print (c);} while (err.available () > 0) {//Print the output of our system callcharacter c = new Character ((char) err.read ()); System.out.print (c);} Ask the process for its exitvalue. If the process//is not finished, a illegalthreadstateexception//is thrown. If It is finished, we fall through and//the variable finished are set to True.exitvalue = Process.exitvalue (); finished = t Rue;} catch (Illegalthreadstateexception e) {//Process is not finished yet;//Sleep a little to save on CPU Cyclesthread.curren TThread (). Sleep (500);}}} catch (Exception e) {e.printstacktrace ();} finally {try {if (in! = null) {In.close ()}} catch (IOException e) {E.print StackTrace ();} if (err! = null) {try {err.close ();} catch (IOException e) {e.printstacktrace ();}}} return exitvalue;}

　　

Java calling external program blocking code with runtime