gain root permission android

//
// method 1
//

Process p; 
try {
   p = Runtime.getRuntime().exec("su"); 

   DataOutputStream os = new DataOutputStream(p.getOutputStream()); 
   os.writeBytes("echo \"root?\" >/data/temporary.txt\n");


   os.writeBytes("exit\n"); 
   os.flush(); 
   try { 
      p.waitFor(); 
           if (p.exitValue() != 255) { 
              // TODO Code to run on success 
              toastMessage("root"); 
           } 
           else { 
               // TODO Code to run on unsuccessful 
               toastMessage("not root"); 
           } 
   } catch (InterruptedException e) { 
      // TODO Code to run in interrupted exception 
       toastMessage("not root"); 
   } 
} catch (IOException e) { 
   // TODO Code to run in input/output exception 
    toastMessage("not root"); 
}