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package org.openslx.util;
/**
* A reference holder that will only return the object it is holding if
* the given timeout has not been reached.
* The timeout will start anew if you set this reference to hold a new object,
* or if you retrieve the object, and refreshOnGet is set to true.
*/
public class TimeoutReference<T>
{
private final long timeoutMs;
private final boolean refreshOnGet;
private final T item;
private long deadline;
private boolean invalid;
public TimeoutReference( boolean refreshOnGet, long timeoutMs, T item )
{
this.refreshOnGet = refreshOnGet;
this.item = item;
this.timeoutMs = timeoutMs;
this.deadline = System.currentTimeMillis() + timeoutMs;
}
public TimeoutReference( long timeoutMs, T item )
{
this( false, timeoutMs, item );
}
public synchronized T get()
{
if ( item == null || invalid )
return null;
final long now = System.currentTimeMillis();
if ( deadline < now ) {
invalid = true;
return null;
}
if ( refreshOnGet ) {
deadline = now + timeoutMs;
}
return item;
}
synchronized boolean isInvalid()
{
return invalid;
}
@Override
public int hashCode()
{
return item == null ? super.hashCode() : item.hashCode();
}
@Override
public boolean equals( Object o )
{
return ( this == o || this.item == o || ( o != null && o.equals( this.item ) ) );
}
}
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