Java Set Copy copy(Set<T> data)

Description

Copies the given Set into a new Set .

License

Open Source License

Parameter

Parameter	Description
T	the type of the entries of the set
data	the given set

Return

If the given set was empty, a is returned
If the given set contained only one element, a , containing said element, is returned
If the given set contained more than one element, a , containing the elements of the given set, is returned.

Declaration

public static <T> Set<T> copy(Set<T> data)

Method Source Code

//package com.java2s;
/******************************************************************************
 * Copyright (c) 2007 Stefan Franke, Robert Hanussek, Benjamin Keil,          *
 *                    Steffen Kie?, Johannes Langauf,                         *
 *                    Christoph Marian M?ller, Igor Podolskiy,                *
 *                    Tilmann Scheller, Michael Starzmann, Markus Wittlinger  *
 * All rights reserved. This file may be used, modifies and redistributed     *
 * under the terms of either the Eclipse Public License v1.0 which            *
 * accompanies this distribution and is available at                          *
 * http://www.eclipse.org/legal/epl-v10.html or the MIT license, available at *
 * http://www.opensource.org/licenses/mit-license.php                         *
 ******************************************************************************/

import java.util.*;

public class Main {
    /**/*from  w w w  .  j  ava 2s  . co  m*/
     * Copies the given {@link Set} into a new {@link Set}.<br>
     * 
     * 
     * @param <T>
     *            the type of the entries of the set
     * @param data
     *            the given set
     * @return If the given set was empty, a {@link Collections#emptySet()} is
     *         returned<br>
     *         If the given set contained only one element, a
     *         {@link Collections#singleton(Object)}, containing said element,
     *         is returned <br>
     *         If the given set contained more than one element, a
     *         {@link Collections#unmodifiableSet(Set)}, containing the
     *         elements of the given set, is returned.
     */
    public static <T> Set<T> copy(Set<T> data) {
        final int size = data.size();

        switch (size) {
        case 0:
            return Collections.emptySet();
        case 1:
            return Collections.singleton(data.iterator().next());
        default:
            return Collections.unmodifiableSet(new HashSet<T>(data));
        }
    }

    /**
     * Copies the given {@link List} into a new {@link List}.<br>
     * 
     * 
     * @param <T>
     *            the type of the entries of the list
     * @param data
     *            the given list
     * @return If the given list was empty, a {@link Collections#emptyList()} is
     *         returned<br>
     *         If the given list contained only one element, a
     *         {@link Collections#singletonList(Object)}, containing said
     *         element, is returned <br>
     *         If the given list contained more than one element, a
     *         {@link Collections#unmodifiableList(List)}, containing the
     *         elements of the given list, is returned.
     */
    public static <T> List<T> copy(List<T> data) {
        final int size = data.size();

        switch (size) {
        case 0:
            return Collections.emptyList();
        case 1:
            return Collections.singletonList(data.get(0));
        default:
            return Collections.unmodifiableList(new ArrayList<T>(data));
        }
    }

    /**
     * Copies the given {@link Map} into a new {@link Map}.<br>
     * 
     * @param <A>
     *            the type of the keys of the map
     * @param <B>
     *            the type of the values of the map
     * @param data
     *            the given map
     * @return If the given map was empty, a {@link Collections#emptyMap()} is
     *         returned<br>
     *         If the given map contained only one entry, a
     *         {@link Collections#singletonMap(Object, Object)}, containing
     *         said entry, is returned <br>
     *         If the given map contained more than one element, a
     *         {@link Collections#unmodifiableMap(Map)}, containing the entries
     *         of the given map, is returned.
     */
    public static <A, B> Map<A, B> copy(Map<A, B> data) {
        final int size = data.size();

        switch (size) {
        case 0:
            return Collections.emptyMap();
        case 1:
            final A key = data.keySet().iterator().next();
            return Collections.singletonMap(key, data.get(key));
        default:
            return Collections.unmodifiableMap(new HashMap<A, B>(data));
        }
    }
}

Java Set Copy copy(Set data)