Apache Common 包学习：常用集合类Collections4学习

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Apache Common 包学习：常用集合类Collections4学习

Maven依赖

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<dependencies>
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-collections4</artifactId>
        <version>4.3</version>
    </dependency>
</dependencies>

CollectionUtils

<O> Collection<O> subtract(final Iterable<? extends O> a, final Iterable<? extends O> b)

a是做差集运算的左集，b是做差集运算的右集，下面是一个例子

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public class Demo {

    private static final Logger LOGGER = LoggerFactory.getLogger(Demo.class);

    public static void main(String[] args) {

        Set<Pair<String, String>> allProductDevices = Sets.newHashSet(Pair.of("a", "b"), Pair.of("c", "d"));

        Set<Pair<String, String>> oldProductDevices = Sets.newHashSet(Pair.of("a", "b"), Pair.of("e", "f"));

        List<Pair<String, String>> newProductDevices =
                (ArrayList<Pair<String, String>>) CollectionUtils.subtract(allProductDevices, oldProductDevices);

        List<String> list1 = Lists.newArrayList("a", "b");

        List<String> list2 = Lists.newArrayList("c", "b");

        List<String> list3 = (ArrayList<String>) CollectionUtils.subtract(list1, list2);
    }
}