Thread: Why runtime error?

Hello.
I get a run-time error executing my code. Can anyone tell me why?

Thanks in advance

Here is my class with main():

class ExecDemo{
	   // Date	d = new Date();
 
	   public static void main( String args[] ){
	   Runtime r = Runtime.getRuntime();
	   Process p = null;
 
	    try{
		   p = r.exec("ls");
		   p.waitFor();
	       p=r.exec("ping 8.8.8.8");
	   }
	   catch(Exception e){
		   System.out.println("Error executing ps");
	   }//end try..catch block
	   System.out.println("ps returned " + p.exitValue());	
	   System.out.println("Total Memory is: " + r.totalMemory());
	   System.out.println("Total Memory is: " + System.getProperty("CPU"));
 
	}//end main( string args[] )
}

This is my screen output:

soheil@soheil-desktop:~/test_suite$ java ExecDemo
Exception in thread "main" java.lang.IllegalThreadStateException: process hasn't exited
at java.lang.UNIXProcess.exitValue(UNIXProcess.java:1 88)
at ExecDemo.main(ExecDemo.java:25)
soheil@soheil-desktop:~/test_suite$

I called waitFor() for the 2nd instance of the process, but nothing appeared at the output.
Similar;y, I wrote:

p = r.exec("top -n1");
p.waitFor();

again, with no result whatsoever.

Originally Posted by KevinWorkman

What output are you expecting?

I expect the same output as when exdecuting free-m or top -n1 from the command prompt/terminal

--- Update ---

I look for a call similar to C++ system(), most efficient.

exec("top", "-n1"); errors at compile time

This is the only info I get:

ExecDemo.java:20: cannot find symbol
symbol : method exec(java.lang.String,java.lang.String)
location: class java.lang.Runtime
p = r.exec("top" , "-n1");
^
1 error
soheil@soheil-desktop:~/test_suite$

--- Update ---

I need to obtain the memory status + CPU speed

The error message in your last post is simply stating that the Runtime class doesn't have an exec() method with 2 String parameters. See Runtime (Java Platform SE 7 ) for the different variants of the exec() method.

Alternatively, as KevinWorkman suggested, you can use ProcessBuilder to do this. See ProcessBuilder (Java Platform SE 7 ).