import java.lang.Runtime;
import java.lang.Process;

...

class myRuntime {
	void method(String cmd) throws IOException, InterruptedException {
		Process	proc;
		Runtime	run = Runtime.getRuntime();

		System.out.println("Free memory is  " + run.freeMemory());
		run.gc();		// garbage collector
		System.out.println("Free memory is  " + run.freeMemory());
		
		proc = run.exec(cmd);
		proc.waitFor();
		System.out.println("Exit status is " + proc.exitValue());
	}
}