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feilong is a suite of core and expanded libraries that include utility classes, http, excel,cvs, io classes, and much much more.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 com.feilong.lib.collection4.functors;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.collections4.Predicate;

/**
 * Predicate implementation that returns true the first time an object is
 * passed into the predicate.
 * 
 * @param 
 *
 * @since 3.0
 */
public final class UniquePredicate implements Predicate,Serializable{

    /** Serial version UID */
    private static final long serialVersionUID = -3319417438027438040L;

    /** The set of previously seen objects */
    private final Set      iSet             = new HashSet<>();

    /**
     * Factory to create the predicate.
     *
     * @param 
     *            the type that the predicate queries
     * @return the predicate
     * @throws IllegalArgumentException
     *             if the predicate is null
     */
    public static  Predicate uniquePredicate(){
        return new UniquePredicate<>();
    }

    /**
     * Constructor that performs no validation.
     * Use uniquePredicate if you want that.
     */
    public UniquePredicate(){
        super();
    }

    /**
     * Evaluates the predicate returning true if the input object hasn't been
     * received yet.
     *
     * @param object
     *            the input object
     * @return true if this is the first time the object is seen
     */
    @Override
    public boolean evaluate(final T object){
        return iSet.add(object);
    }

}