org.eclipse.xtext.xbase.lib.MapExtensions.java Source code

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Here is the source code for org.eclipse.xtext.xbase.lib.MapExtensions.java

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/*******************************************************************************
 * Copyright (c) 2011 itemis AG (http://www.itemis.eu) and others.
 * 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
 *******************************************************************************/
package org.eclipse.xtext.xbase.lib;

import java.util.Map;

import org.eclipse.xtext.xbase.lib.Functions.Function1;
import org.eclipse.xtext.xbase.lib.Functions.Function2;
import org.eclipse.xtext.xbase.lib.Procedures.Procedure2;
import org.eclipse.xtext.xbase.lib.Procedures.Procedure3;
import org.eclipse.xtext.xbase.lib.internal.FunctionDelegate;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Predicate;
import com.google.common.collect.Maps;

/**
 * This is an extension library for {@link Map maps}.
 * 
 * @author Sebastian Zarnekow - Initial contribution and API
 */
@GwtCompatible
public class MapExtensions {

    /**
     * Applies the given {@code procedure} for each {@link java.util.Map.Entry key value pair} of the given {@code map}. 
     * 
     * @param map
     *            the map. May not be <code>null</code>.
     * @param procedure
     *            the procedure. May not be <code>null</code>.
     */
    public static <K, V> void forEach(Map<K, V> map, Procedure2<? super K, ? super V> procedure) {
        if (procedure == null)
            throw new NullPointerException("procedure");
        for (Map.Entry<K, V> entry : map.entrySet()) {
            procedure.apply(entry.getKey(), entry.getValue());
        }
    }

    /**
     * Applies the given {@code procedure} for each {@link java.util.Map.Entry key value pair} of the given {@code map}. 
     * The procedure takes the key, the value and a loop counter. If the counter would overflow, {@link Integer#MAX_VALUE}
     * is returned for all subsequent pairs. The first pair is at index zero.
     * 
     * @param map
     *            the map. May not be <code>null</code>.
     * @param procedure
     *            the procedure. May not be <code>null</code>.
     */
    public static <K, V> void forEach(Map<K, V> map, Procedure3<? super K, ? super V, ? super Integer> procedure) {
        if (procedure == null)
            throw new NullPointerException("procedure");
        int i = 0;
        for (Map.Entry<K, V> entry : map.entrySet()) {
            procedure.apply(entry.getKey(), entry.getValue(), i);
            if (i != Integer.MAX_VALUE)
                i++;
        }
    }

    /**
     * <p>
     * Returns a filtered live view on top of the original map. Changes to one affect the other.
     * </p>
     * 
     * <p>
     * The mapping is done lazily. That is, subsequent access of the values in the map will repeatedly apply the
     * transformation. Characteristics of the original map, such as iteration order, are left intact. Changes in the
     * original map are reflected in the result map. The results supports removal if the original map supports removal.
     * </p>
     * 
     * @param original
     *            the original map. May not be <code>null</code>.
     * @param predicate
     *            the predicate. May not be <code>null</code>.
     * @return a filtered view on top of the original map. Never <code>null</code>.
     */
    public static <K, V> Map<K, V> filter(Map<K, V> original,
            final Function2<? super K, ? super V, Boolean> predicate) {
        if (predicate == null)
            throw new NullPointerException("predicate");
        return Maps.filterEntries(original, new Predicate<Map.Entry<K, V>>() {
            @Override
            public boolean apply(Map.Entry<K, V> input) {
                Boolean result = predicate.apply(input.getKey(), input.getValue());
                return result.booleanValue();
            }
        });
    }

    /**
     * <p>Returns a map that performs the given {@code transformation} for each value of {@code original} when requested.</p>
     * 
     * <p>The mapping is done lazily. That is, subsequent access of the values in the map will repeatedly apply the
     * transformation. Characteristics of the original map, such as iteration order, are left intact. Changes in the
     * original map are reflected in the result map. The results supports removal if the original map supports removal.</p>
     * 
     * @param original
     *            the original map. May not be <code>null</code>.
     * @param transformation
     *            the transformation. May not be <code>null</code>.
     * @return a map with equal keys but transformed values. Never <code>null</code>.
     * @since 2.4
     */
    public static <K, V1, V2> Map<K, V2> mapValues(Map<K, V1> original,
            Function1<? super V1, ? extends V2> transformation) {
        return Maps.transformValues(original, new FunctionDelegate<V1, V2>(transformation));
    }

}