Converts a collection to a list by either casting or creating a concrete list depending on the type of collection given. - Java java.util

Java examples for java.util:Collection Convert

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Description

Converts a collection to a list by either casting or creating a concrete list depending on the type of collection given.

Demo Code


//package com.book2s;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

public class Main {
    public static void main(String[] argv) {
        Collection c = java.util.Arrays.asList("asdf", "book2s.com");
        System.out.println(listFromCollection(c));
    }//  www .  java 2s . c  o  m

    /**
     * Converts a collection to a list by either casting or creating a concrete
     * list depending on the type of collection given.
     * @param <T> The type of the elements in the collection.
     * @param c the collection. If <code>null</code>, <code>null</code> is
     *        returned.
     * @return {@link List} containing the same elements as the given
     *         {@link Collection} param.
     */
    public static <T> List<T> listFromCollection(Collection<T> c) {
        if (c == null)
            return null;
        if (c.size() < 1) {
            return new ArrayList<T>(0);
        }
        return (c instanceof List<?>) ? (List<T>) c : new ArrayList<T>(c);
    }
}

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