用集合A={1，2，3，4}，B={1，3，5，9，11}，选择合适的容器类，用Java编写程序求A与B的交/并/差

可以使用Java中的Set集合类来实现。

交集：

Set<Integer> setA = new HashSet<>(Arrays.asList(1, 2, 3, 4));
Set<Integer> setB = new HashSet<>(Arrays.asList(1, 3, 5, 9, 11));
Set<Integer> intersection = new HashSet<>(setA);
intersection.retainAll(setB);
System.out.println("A与B的交集为：" + intersection);

并集：

Set<Integer> setA = new HashSet<>(Arrays.asList(1, 2, 3, 4));
Set<Integer> setB = new HashSet<>(Arrays.asList(1, 3, 5, 9, 11));
Set<Integer> union = new HashSet<>(setA);
union.addAll(setB);
System.out.println("A与B的并集为：" + union);

差集：

Set<Integer> setA = new HashSet<>(Arrays.asList(1, 2, 3, 4));
Set<Integer> setB = new HashSet<>(Arrays.asList(1, 3, 5, 9, 11));
Set<Integer> diff = new HashSet<>(setA);
diff.removeAll(setB);
System.out.println("A与B的差集为：" + diff);