mem1 = r.freeMemory();
System.out.println("Initial free memory: " + mem1);
r.gc();
mem1 = r.freeMemory();
System.out.println("Free memory after garbage collection: "
+ mem1);
for(int i=0; i<1000; i++)
someints[i] = new Integer(i); // allocate integers
mem2 = r.freeMemory();
System.out.println("Free memory after allocation: "
+ mem2);
System.out.println("Memory used by allocation: "
+ (mem1-mem2));
// discard Integers
for(int i=0; i<1000; i++) someints[i] = null;
r.gc(); // request garbage collection
mem2 = r.freeMemory();
System.out.println("Free memory after collecting" +
" discarded Integers: " + mem2);
}
}
Sample output from this program is shown here (of course, your actual results may vary):
Total memory is: 1048568
Initial free memory: 751392
Free memory after garbage collection: 841424
Free memory after allocation: 824000
Memory used by allocation: 17424
Free memory after collecting discarded Integers: 842640
Executing Other Programs
In safe environments, you can use Java to execute other heavyweight processes (that is,
programs) on your multitasking operating system. Several forms of the exec( ) method
allow you to name the program you want to run as well as its input parameters. The exec( )
method returns a Process object, which can then be used to control how your Java program
interacts with this new running process. Because Java can run on a variety of platforms and
under a variety of operating systems, exec( ) is inherently environment-dependent.
The following example uses exec( ) to launch notepad, Windows' simple text editor.
Obviously, this example must be run under the Windows operating system.
// Demonstrate exec().
class ExecDemo {
public static void main(String args[]) {
Runtime r = Runtime.getRuntime();
Process p = null;
Search WWH :
