65 lines
1.6 KiB
Java
65 lines
1.6 KiB
Java
package fr.pandacube.lib.util;
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import java.util.Objects;
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import java.util.function.Supplier;
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/**
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* A Supplier that cache the value the first time it is called.
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*
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* @param <T> the type of the supplied value.
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*/
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public class CachedSupplier<T> implements Supplier<T> {
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private T cachedValue;
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private final Supplier<T> source;
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private boolean cached = false;
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/**
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* Create a lazy value loader that will call the provided supplier to get the value.
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* @param s the supplier from which the value is fetched.
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*/
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public CachedSupplier(Supplier<T> s) {
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source = Objects.requireNonNull(s);
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}
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/**
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* Get the value, from cache or from the source supplier if it's not yet cached.
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* <p>
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* If the provider throws an exception, it will be redirected to the caller as is, and no value will be cached
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* (the next call to this method will execute the supplier again).
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*/
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@Override
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public synchronized T get() {
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if (!cached)
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set(source.get());
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return cachedValue;
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}
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/**
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* Reset the cached value. The next call to {@link #get()} will get the value from the source.
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*/
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public synchronized void reset() {
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cached = false;
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cachedValue = null;
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}
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/**
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* Manually set the value to the provided one.
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* @param value the value to put in the cache.
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*/
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public synchronized void set(T value) {
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cachedValue = value;
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cached = true;
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}
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/**
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* Tells if the value is currently set or not.
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* @return true if the value has been set by calling the method {@link #get()} or {@link #set(Object)} but not yet
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* reset by {@link #reset()}, or false otherwise.
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*/
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public synchronized boolean isSet() {
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return cached;
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}
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}
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