File file=new File(strName+".java");
                        FileOutputStream fos=new FileOutputStream(file);
                        OutputStreamWriter osr=new OutputStreamWriter(fos);
                        BufferedWriter bw=new BufferedWriter(osr);
                        bw.write(text.getText());
                        bw.close();
                        
                        
                        String cmd = "javac ";
                        String param =file.getName();
                        
                        Process child = Runtime.getRuntime().exec(cmd+param); //没有输出
                        //Process   child   =   Runtime.getRuntime().exec( "ipconfig   /all ");   //输出正常
                        try{ Thread.sleep(1000);}
                        catch(Exception ex){ex.printStackTrace();}
                        
                        InputStream is = child.getInputStream();
                        InputStreamReader isr=new InputStreamReader(is);
                        
                        BufferedReader br=new BufferedReader(isr);

                        String str="";
                        while ((str=br.readLine())!=null)
                        {
                           
                            editInformation=editInformation+str+"\r\n";
                        }
                      System.out.println(editInformation);
                      br.close();


  Process child = Runtime.getRuntime().exec(cmd+param); //没有输出
  //Process   child   =   Runtime.getRuntime().exec( "ipconfig   /all ");   //输出正常
 为什么啊？  怎样才能正常输出？