将多个集合合并为一个？

Question

我有以下代码：

Object value = methodOutOfMyControl();        
Collection<LinkedHashSet<String>> values = ((Map) value).values();
Set<String> strings = new HashSet<String>();
for (LinkedHashSet<String> set : values) {
    strings.addAll(set);
}

有没有办法重写这段代码更简洁？

P.S.我用java6

Answer 1

这个看起来更好看：

 Collection<LinkedHashSet<String>> values = ((Map) userPreferenceValue).values();
 Set<String> contraValues = Sets.newHashSet(Iterables.concat(values));

Answer 2

在Java6中我会推荐Guava的FluentIterable:

Object value = methodOutOfMyControl();
Collection<LinkedHashSet<String>> values = ((Map) value).values();

//transformAndConcat is similar to Java 8, Stream.flatMap
final ImmutableSet<String> set = FluentIterable.from(values)
      .transformAndConcat(Functions.identity()).toSet();

或者如果你真的想要一行：

 final ImmutableSet<String> set = FluentIterable.from(
            ((Map<?, LinkedHashSet<String>>) this.methodOutOfMyControl()).values())
        .transformAndConcat(Functions.identity())
        .toSet();

将多个集合合并为一个？

Combine severel collections into one?

java

collections

guava