[Guava] 자주 사용하는 Sets api

https://guava-libraries.googlecode.com/svn/tags/release04/javadoc/com/google/common/collect/Sets.html

Set instace 생성/변환할 때 사용한다. 

Sets.newCopyOnWriteArraySet()

Sets.newConcurrentHashSet()

Sets.newLinkedHashSet()

Sets.newTreeSet()

Sets.newHashSet()

Sets.newHashSetWithExpectedSize(members.size())

Sets.immutableEnumSet(encodeKey)  

가장 많이 유용한 것은 Set간의 intersection, union이다. 

@Test
public void test() {

Set<String> set1 = new HashSet<String>();
set1.add("a");
set1.add("b");
set1.add("c");

Set<String> set2 = new HashSet<String>();
set2.add("c");
set2.add("d");
set2.add("e");

Set<String> intersection = Sets.intersection(set1, set2);
System.out.println(Arrays.toString(intersection.toArray()));

Set<String> union = Sets.union(set1, set2);
System.out.println(Arrays.toString(union.toArray()));

}

결과

[c]

[b, c, a, d, e]