/*
* Copyright 2013 Guidewire Software, Inc.
*/
package gw.util.concurrent;
/**
* Implements the lazy initialization pattern.
* No locking of any kind is used.
*/
public abstract class LocklessLazyVar<T>
{
protected final static Object NULL = new Object();
private volatile T _val = null;
/**
* @return the value of this lazy var, created if necessary
*/
public final T get()
{
T result = _val;
if(result == NULL) {
return null;
}
if( result == null )
{
result = init();
if (result == null) {
_val = (T)NULL;
} else {
_val = result;
}
}
return result;
}
protected abstract T init();
/**
* Clears the variable, forcing the next call to {@link #get()} to re-calculate
* the value.
*/
public final T clear()
{
T hold = _val;
_val = null;
return hold;
}
protected void initDirectly( T val )
{
_val = val;
}
public boolean isLoaded() {
return _val != null;
}
/**
* A simple init interface to make LockingLazyVar's easier to construct
* from gosu.
*/
public static interface LazyVarInit<Q> {
public Q init();
}
/**
* Creates a new LockingLazyVar based on the type of the LazyVarInit passed in.
* This method is intended to be called with blocks from Gosu.
* @deprecated Of dubious value. Use your own null check. In some cases in Gosu, this is used to pass a block and an interface would be better in those cases.
*/
@Deprecated
public static <Q> LocklessLazyVar<Q> make( final LazyVarInit<Q> init ) {
return new LocklessLazyVar<Q>(){
protected Q init()
{
return init.init();
}
};
}
}