com.swtxml.util.lang.CollectionUtils.java Source code

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Here is the source code for com.swtxml.util.lang.CollectionUtils.java

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/*******************************************************************************
 * Copyright (c) 2008 Ralf Ebert
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Ralf Ebert - initial API and implementation
 *******************************************************************************/
package com.swtxml.util.lang;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.commons.lang.StringUtils;

import com.swtxml.util.reflector.ReflectorException;

public class CollectionUtils {

    /**
     * Returns the first element from iterable for which filter.match(element)
     * returned true.
     */
    public static <A> A find(Iterable<? extends A> iterable, IFilter<A> filter) {
        for (A a : iterable) {
            if (filter.match(a)) {
                return a;
            }
        }
        return null;
    }

    /**
     * Returns a new collection containing all elements from collection for
     * which filter.match(element) returned true.
     */
    @SuppressWarnings("unchecked")
    public static <A> Collection<A> select(Collection<? extends A> collection, IFilter<A> filter) {
        Collection<A> resultList = createCollection(collection);
        for (A a : collection) {
            if (filter.match(a)) {
                resultList.add(a);
            }
        }
        return resultList;
    }

    /**
     * Returns a new collection containing the result from
     * function.apply(element) for all elements from collection.
     */
    @SuppressWarnings("unchecked")
    public static <FROM, TO> Collection<TO> collect(Collection<? extends FROM> collection,
            IFunction<FROM, TO> function) {
        Collection<TO> resultList = createCollection(collection);
        for (FROM a : collection) {
            resultList.add(function.apply(a));
        }
        return resultList;
    }

    /**
     * Returns a new list containing the result from function.apply(element) for
     * all elements from list.
     */
    public static <FROM, TO> List<TO> collect(List<? extends FROM> list, IFunction<FROM, TO> function) {
        List<TO> resultList = new ArrayList<TO>();
        for (FROM a : list) {
            resultList.add(function.apply(a));
        }
        return resultList;
    }

    /**
     * Returns a comma-separated String of the collection toString values
     * alphabetically sorted by value.
     */
    public static String sortedToString(Collection<?> collection) {
        List<String> strings = new ArrayList<String>(collect(collection, Functions.TO_STRING));
        Collections.sort(strings);
        return StringUtils.join(strings, ", ");
    }

    @SuppressWarnings("unchecked")
    private static Collection createCollection(Collection original) {
        if (original instanceof Set) {
            return new HashSet();
        }
        if (original instanceof Collection) {
            return new ArrayList();
        }
        throw new ReflectorException("Unknown collection type: " + original.getClass());
    }

}