Kotlin + Jline 2, 58 bytes
{print(jline.TerminalFactory.get().run{"$width $height"})}
Because why not. Turns out the standard lib actually has no way to determine console size so pulling in a library is required, lest you want to gold launching another process and parsing the input stream... would be a shame if somebody did that..
Whoops I had too much free time.
(noncompeting) Java 8 (SE only), Windows, 270 bytes
Marked as noncompeting due to arbitrary restriction of using no external libraries.
interface A{static void main(String[]a)throws Exception{Object[]r=new java.io.BufferedReader(new java.io.InputStreamReader(Runtime.getRuntime().exec("cmd /c mode").getInputStream())).lines().map(s->s.replaceAll("[^\\d]+","")).toArray();System.out.print(r[3]+" "+r[4]);}}
Ungolfed:[would be a shame if somebody did that..
interface A {
static void main(String[] a) throws Exception {
Object[] r = new java.io.BufferedReader(
new java.io.InputStreamReader(
Runtime.getRuntime().exec("cmd /c mode")
.getInputStream()
)
).lines().map(s -> s.replaceAll("[^\\d]+", "")).toArray();
System.out.print(r[3] + " " + r[4]);
}
}