53 lines
1.3 KiB
Java
53 lines
1.3 KiB
Java
package fr.pandacube.lib.core.util;
|
|
|
|
import java.util.Objects;
|
|
|
|
/**
|
|
* 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;
|
|
}
|
|
|
|
|
|
@FunctionalInterface
|
|
public interface SupplierException<T> {
|
|
public T get() throws Exception;
|
|
}
|
|
|
|
}
|