com.jfreeman.attribute.InheritedAttribute Maven / Gradle / Ivy

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package com.jfreeman.attribute;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import com.jfreeman.lazy.LateBound;
import com.jfreeman.lazy.Lazy;

/**
 * @author jfreeman
 */
public class InheritedAttribute
    implements Attribute
{
    private final Map> _attrs = new ConcurrentHashMap<>();

    private LateBound getOrCreate(N node) {
        LateBound attr = _attrs.get(node);
        if (attr == null) {
            attr = LateBound.of();
            _attrs.put(node, attr);
        }
        return attr;
    }

    /**
     * {@inheritDoc}
     *
     * May be called before the node's value has been
     * {@link #set(Object, Lazy)}.
     */
    @Override
    public Lazy get(N node) {
        return getOrCreate(node);
    }

    @Override
    public void set(N node, Lazy value) {
        getOrCreate(node).bind(value);
    }
}