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package scala.actors.threadpool.helpers;
import java.util.Collection;
import java.util.ArrayList;
import java.util.List;
/**
* Simple linked list queue used in FIFOSemaphore.
* Methods are not synchronized; they depend on synch of callers.
* Must be public, since it is used by Semaphore (outside this package).
* NOTE: this class is NOT present in java.util.concurrent.
**/
public class FIFOWaitQueue extends WaitQueue implements java.io.Serializable {
private final static long serialVersionUID = 2416444691925378811L;
protected transient WaitNode head_ = null;
protected transient WaitNode tail_ = null;
public FIFOWaitQueue() {}
public void insert(WaitNode w) {
if (tail_ == null)
head_ = tail_ = w;
else {
tail_.next = w;
tail_ = w;
}
}
public WaitNode extract() {
if (head_ == null)
return null;
else {
WaitNode w = head_;
head_ = w.next;
if (head_ == null)
tail_ = null;
w.next = null;
return w;
}
}
public void putBack(WaitNode w) {
w.next = head_;
head_ = w;
if (tail_ == null)
tail_ = w;
}
public boolean hasNodes() {
return head_ != null;
}
public int getLength() {
int count = 0;
WaitNode node = head_;
while (node != null) {
if (node.waiting) count++;
node = node.next;
}
return count;
}
public Collection getWaitingThreads() {
List<Thread> list = new ArrayList<Thread>();
int count = 0;
WaitNode node = head_;
while (node != null) {
if (node.waiting) list.add(node.owner);
node = node.next;
}
return list;
}
public boolean isWaiting(Thread thread) {
if (thread == null) throw new NullPointerException();
for (WaitNode node = head_; node != null; node = node.next) {
if (node.waiting && node.owner == thread) return true;
}
return false;
}
}
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