Exemplo

public static void main( String[] args ){
Lock lock = new Lock();
final Consumer consumer = new Consumer( lock );
final Producer producer = new Producer( lock );

(new Thread( new Runnable() {
public void run() {
consumer.consume();
}
})).start();

(new Thread( new Runnable() {
public void run() {
producer.produce();
}
})).start();
}

public static final class Lock {
public Lock() {
super();
lock();
}
public boolean isAvailable() {
return available;
}
public void lock() {
available = false;
}
public void unlock() {
available = true;
}
private boolean available = false;
}

public static final class Consumer {
public Consumer( Lock lock ) {
this .lock = lock;
}

public void consume() {
System.out.println( "Consumidor: consume foi chamado" ); //$NON-NLS-1$
while ( !lock.isAvailable() ) {
System.out.println( "Consumidor: hibernando..." ); //$NON-NLS-1$
try { Thread.sleep( 1000 ); } catch (InterruptedException e) {}
}
System.out.println( "Consumidor: saindo" ); //$NON-NLS-1$
}

private Lock lock;
}

public static final class Producer {
public Producer( Lock lock ) {
this .lock = lock;
}
public void produce() {
System.out.println( "Produtor: produce foi chamado" ); //$NON-NLS-1$
try { Thread.sleep( 5000 ); } catch (InterruptedException e) {}
System.out.println( "Produtor: desbloqueando..." ); //$NON-NLS-1$
lock.unlock();
System.out.println( "Produtor: saindo" ); //$NON-NLS-1$
}
private Lock lock;
}

Solução

Altere while()/sleep() para wait()/notify().

public static void main( String[] args ){
Lock lock = new Lock();
final Consumer consumer = new Consumer( lock );
final Producer producer = new Producer( lock );

(new Thread( new Runnable() {
public void run() {
consumer.consume();
}
})).start();

(new Thread( new Runnable() {
public void run() {
producer.produce();
}
})).start();
}

public static final class Lock {
public Lock() {
super();
lock();
}
public boolean isAvailable() {
return available;
}
public void lock() {
available = false;
}
public void unlock() {
available = true;
}
private boolean available = false;
}

public static final class Consumer {
public Consumer( Lock lock ) {
this .lock = lock;
}

public void consume() {
System.out.println( "Consumidor: consume foi chamado" ); //$NON-NLS-1$
synchronized ( lock ) {
while ( !lock.isAvailable() ) {
System.out.println( "Consumidor: aguardando..." ); //$NON-NLS-1$
try {
lock.wait();
} catch (InterruptedException e) {}
}
}
System.out.println( "Consumidor: saindo" ); //$NON-NLS-1$
}
private Lock lock;
}

public static final class Producer {
public Producer( Lock lock ) {
this .lock = lock;
}
public void produce() {
System.out.println( "Produtor: produce foi chamado" ); //$NON-NLS-1$
System.out.println( "Produtor: desbloqueando..." ); //$NON-NLS-1$
synchronized ( lock ) {
lock.unlock();
lock.notifyAll();
}
System.out.println( "Produtor: saindo" ); //$NON-NLS-1$
}
private Lock lock;
}