com.sun.javafx.css.ImmutablePseudoClassSetsCache Maven / Gradle / Ivy
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package com.sun.javafx.css;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import javafx.css.PseudoClass;
/**
* A cache for immutable sets of {@link PseudoClass}es.
*/
public class ImmutablePseudoClassSetsCache {
private static final Map, Set> CACHE = new HashMap<>();
/**
* Returns an immutable set of {@link PseudoClass}es.
*
* Note: this method may or may not return the same instance for the same set of
* {@link PseudoClass}es.
*
* @param pseudoClasses a set of {@link PseudoClass} to make immutable, cannot be {@code null}
* @return an immutable set of {@link PseudoClass}es, never {@code null}
* @throws NullPointerException when {@code pseudoClasses} is {@code null} or contains {@code null}s
*/
public static Set of(Set pseudoClasses) {
Set cachedSet = CACHE.get(Objects.requireNonNull(pseudoClasses, "pseudoClasses cannot be null"));
if (cachedSet != null) {
return cachedSet;
}
Set copy = Set.copyOf(pseudoClasses);
CACHE.put(copy, copy);
return copy;
}
}