io.yields.math.framework.property.SortedProperty.java Source code

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Here is the source code for io.yields.math.framework.property.SortedProperty.java

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/*
 * Copyright 2015 by Yields.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.yields.math.framework.property;

import org.apache.commons.lang.Validate;

import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

import io.yields.math.framework.FunctionalContext;
import io.yields.math.framework.Property;

public class SortedProperty<T extends Comparable<T>> implements Property<List<T>> {

    private static final String LABEL = "sorted";

    private boolean increasing;
    private Comparator<T> comparator;
    private static final double EPS = 1.e-8;
    private final String explanation;

    protected SortedProperty(boolean increasing, Class<T> clazz, String explanation) {
        this.increasing = increasing;
        if (clazz.equals(Double.class) || clazz.equals(double.class)) {
            this.comparator = new Comparator<T>() {
                @Override
                public int compare(T o1, T o2) {
                    return compareDouble(o1, o2);
                }
            };
        } else {
            this.comparator = new Comparator<T>() {
                @Override
                public int compare(T o1, T o2) {
                    return o1.compareTo(o2);
                }
            };
        }
        this.explanation = explanation;
    }

    @Override
    public boolean isValid(List<T> value, FunctionalContext<List<T>> context) {
        Validate.notEmpty(value, "An empty collection cannot be ordered.");
        int sign = increasing ? 1 : -1;
        List<T> sorted = value.stream().sorted((t1, t2) -> sign * t1.compareTo(t2)).collect(Collectors.toList());
        return IntStream.range(0, value.size())
                .allMatch(index -> comparator.compare(sorted.get(index), value.get(index)) == 0);
    }

    @Override
    public String getLabel() {
        return LABEL;
    }

    private int compareDouble(Object tx, Object ty) {
        double x = (double) tx;
        double y = (double) ty;
        if (Math.abs(x - y) < EPS) {
            return 0;
        } else {
            return Double.compare(x, y);
        }
    }

    @Override
    public String getExplanation() {
        return explanation;
    }
}