public class GCTest {

final int NELEMS = 50000;

void eatMemory() {

int[] intArray = new int[NELEMS];

for (int i=0; i<NELEMS; i++) {
intArray[i] = i;
}

}

public static void main (String[] args) {

GCTest gct = new GCTest();

// Step 1: get a Runtime object
Runtime r = Runtime.getRuntime();

// Step 2: determine the current amount of free memory
long freeMem = r.freeMemory();
System.out.println("free memory before creating array: " + freeMem);

// Step 3: consume some memory
gct.eatMemory();

// Step 4: determine amount of memory left after consumption
freeMem = r.freeMemory();
System.out.println("free memory after creating array: " + freeMem);

// Step 5: run the garbage collector, then check freeMemory
r.gc();
freeMem = r.freeMemory();
System.out.println("free memory after running gc(): " + freeMem);

}

}