org.joo.libra.common.BinaryPredicate Maven / Gradle / Ivy

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package org.joo.libra.common;

import org.joo.libra.PredicateContext;

/**
 * Abstract class for any predicate with 2 inputs. It wraps the evaluation with
 * following conditions:
 * 
 * 
 * - If both objects are null, it will return true
 * - If one object is null, but the other is not, it will return false
 * 
 * 
 * If none of the above conditions are matched, it will let the subclasses
 * determine.
 * 
 * @author griever
 *
 */
public abstract class BinaryPredicate implements CompositionPredicate {

	private HasValue one;

	private HasValue other;

	public BinaryPredicate(final HasValue one, final HasValue other) {
		this.one = one;
		this.other = other;
	}

	@Override
	public boolean satisfiedBy(final PredicateContext context) {
		T theOne = one != null ? one.getValue(context) : null;
		H theOther = other != null ? other.getValue(context) : null;
		if (theOne == null && theOther == null)
			return true;
		if (theOne == null || theOther == null)
			return false;
		return doSatisifiedBy(theOne, theOther);
	}

	protected abstract boolean doSatisifiedBy(T one, H other);

	public String toString() {
		String name = getClass().getSimpleName().replaceAll("Predicate", "").toUpperCase();
		return name + "(" + one + "," + other + ")";
	}
}