Java.lang.Process input stream waiting until process is complete to print

Question

I have tried to simplify this problem as much as possible. Basically, I have a java.lang.Process which executes a simple C program.
test.c
#include <stdio.h>
#include <unistd.h>
int main()
  printf("foo\n");
  sleep(2);
  printf("bar\n");
...The process has an input stream and error stream handler each on a separate thread. I have tried both buffered and unbuffered (BufferedReader, BufferedInputStream, InputStreamReader...) stream handlers. Both produce the same problem of waiting until the process has exited to receive anything from the process's streams.
The only time this does not happen is when I call fflush(stdout); after each printf(). This can't be a solution because the real application calls a massive C application which would require thousands of fflush()'s to be added. What is causing this to happen? This doesn't happen when the C program is executed from the shell. Is there a way the InputStream can be forced to extract from the stream?

Answer 1

hi.....
I have closed the output stream of the process as you told me to do...
The hitch is that, if my program contains only printf() statements,it works fine
as soon as scanf() statement is encountered within the C code,it is totally neglected,and the output comes as if no scanf() statement existed in the C code.
Consequently the thread doesnt wait for input which was bound for scanf() from the thread
the code...
    public void run()
     try
         PrintWriter out = new PrintWriter(socket.getOutputStream(),true);
         BufferedReader in = new BufferedReader(
                        new InputStreamReader(
                        socket.getInputStream()));
         try
                 Process p;
          p=new ProcessBuilder("./a.out").start();
                 PrintWriter exOut=null;
                 BufferedReader exIn=null;
          exOut = new PrintWriter(p.getOutputStream(),true);
          exIn = new BufferedReader(
                       new InputStreamReader(
                       p.getInputStream()));
              //String inputLine="", outputLine="";        
              String str="";
                 int c;          
              while(true)                   
                    //System.out.println("In While");
              str="";exOut.close();                  
                    while((c=exIn.read())!=-1)
                             str=str+(char)(c);
                                System.out.print(str);
                    str=str+(char)(0);
                    System.out.print(str+"outside");
                    out.print(str);
                    sleep(100);
                    try
                        int x=p.exitValue();
                          out.print(str);
               System.out.print("Bye 1");
                        String str1="Bye"+(char)(0);
               out.println(str1);              
               break;
                    catch(IllegalThreadStateException e)
                        //System.out.println("The Process has not ended yet");
                    //str=str+((char)-1);
                    //System.out.print(str+"Control reaches here too");
                    str="";
                    exOut = new PrintWriter(p.getOutputStream(),true);//I have tried to run the program without this also but the effect is the same
                    while((c=in.read())!=-1)
                        str=str+(char)(c);                                    
                    if(str.contentEquals(""))
                            System.out.print("Bye 2");
                            String str1="Bye"+(char)(0);
                            out.println(str1); 
                            p.destroy();
                            exOut.close();
                            exIn.close();
                            out.close();
                            in.close();        
                            socket.close();
                            break;
                    //str=str+(char)(0);
              exOut.print(str);
                    try
                        int x=p.exitValue();
                        System.out.print("Bye 3");
                        String str1="Bye"+(char)(0);
               out.println(str1);
                        break;
                    catch(IllegalThreadStateException e)
                        //System.out.println("The Process has not ended yet");
              /*while ((inputLine = in.readLine()) != null)
                    exOut.println(inputLine);
                    outputLine=exIn.readLine();
                    //outputLine=inputLine;
                    //out.println(outputLine);}*/                   
         exOut.close();
         exIn.close();
         catch(IOException e)
              System.err.println("Accept failed."+e);
         out.close();
         in.close();        
         socket.close();
     catch (Exception e)
         e.printStackTrace();
}