Listing 1
/** Interface for a Generic Container */
interface Container {
public final static int SIZE = 100;
public abstract void store(Object o);
public abstract Object retrieve();
}

/** Base class defines: put and get methods */
public abstract class BoundedContainer
implements Container {

protected int currentSize = 0;
/** put adds an object to container */
public synchronized void put(Object o) {
while (currentSize == SIZE) {
try {
wait();
}
catch (Exception e) { }
}
store(o);
currentSize++;
if (currentSize == 1)
notify();
}
/** get removes an object from container */
public synchronized Object get() {
while (currentSize == 0) {
try {
wait();
}
catch (Exception e) { }
}
Object o = retrieve();
currentSize--;
if (currentSize == SIZE - 1)
notify();
return o;
}
/** isEmpty defines the state */
public synchronized boolean isEmpty() {
return (currentSize == 0);
}
}

Listing 2
/** Extended class adds a new method: gget */
public abstract class ExtBoundedContainer
extends BoundedContainer {

protected boolean lastGet = false;
/** put records the use of get method
and uses the superclass method */
public synchronized void put(Object o) {
super.put(o);
lastGet = false;
}
/** get records its invocation
and uses the superclass method */
public synchronized Object get() {
Object o = super.get();
lastGet = true;
return o;
}
/** gget implements the fuctionality required
in Matsuoka's problem [2] */
public synchronized Object gget() {
while (currentSize == 0 || lastGet == false) {
try {
wait();
}
catch (Exception e) { }
}
return get();
}
}