PandaLib/pandalib-util/src/main/java/fr/pandacube/lib/util/LazyOrException.java
2022-07-20 13:28:01 +02:00

49 lines
1.2 KiB
Java

package fr.pandacube.lib.util;
import java.util.Objects;
import fr.pandacube.lib.util.ThrowableUtil.SupplierException;
/**
* Represents a lazy loaded value.
*
* The value will be computed using the Supplier provided in the
* constructor, only the first time the {@link #get()} method is
* called.
*
* @param <T> the type of the enclosed value.
*/
public class LazyOrException<T> {
private T cachedValue;
private final SupplierException<T> supplier;
private boolean cached = false;
public LazyOrException(SupplierException<T> s) {
supplier = Objects.requireNonNull(s);
}
/**
* Get the wrapped value, from cache or from the provider if it is not yet cached.
*
* If the provider throws an exception, it will be redirected to the caller as is, and no value will be cached (the next call to this method will
* execute the supplier again).
*/
public synchronized T get() throws Exception {
if (!cached) // check outside synchronized method to reduce useless synchronization if value is already cached
set(supplier.get());
return cachedValue;
}
public synchronized void reset() {
cached = false;
cachedValue = null;
}
public synchronized void set(T value) {
cachedValue = value;
cached = true;
}
}