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The James core module is part of the James framework for optimization using local search metaheuristics in Java. The core contains general components to model problems, objectives and constraints, as well as generic algorithms to solve the problems. Moreover, the core provides implementations of specific utilities for subset selection.

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//  Copyright 2014 Herman De Beukelaer
//
//  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 org.jamesframework.core.problems;

import org.jamesframework.core.problems.solutions.Solution;

/**
 * Interface of a problem with a generic solution type. Contains methods to evaluate or validate a solution and
 * to create a random solution. Also indicates whether the evaluations are to be maximized or minimized.
 * 
 * @author Herman De Beukelaer
 * @param  the solution type that corresponds to this problem, required to extend {@link Solution}
 */
public interface Problem {
    
    /**
     * Evaluates a given solution. The computed score reflects the quality of the solution;
     * depending on whether scores are maximized (or minimized), higher (respectively lower)
     * scores indicate improvement.
     * 
     * @see #isMinimizing()
     * @param solution the solution to evaluate
     * @return evaluation of the solution
     */
    public double evaluate(SolutionType solution);
    
    /**
     * Indicates whether the given solution should be rejected during search,
     * regardless of its evaluation. This method may for example be used to
     * discard solutions that do not satisfy imposed constraints.
     * 
     * @param solution solution to verify
     * @return true if the given solution should be rejected
     */
    public boolean rejectSolution(SolutionType solution);
    
    /**
     * Indicates whether scores are being minimized or maximized.
     * 
     * @return true if scores are being minimized
     */
    public boolean isMinimizing();
    
    /**
     * Creates a random solution. Such random solutions can for example be used as initial solution
     * for neighbourhood searches.
     * 
     * @return a random solution
     */
    public SolutionType createRandomSolution();
    
}