使用apache的CollectionUtils工具类

String[] arrayA = new String[] { "1", "2", "3", "4"};
String[] arrayB = new String[] { "3", "4", "5", "6" };
List<String> listA = Arrays.asList(arrayA);
List<String> listB = Arrays.asList(arrayB);

//1、并集 union
System.out.println(CollectionUtils.union(listA, listB));
//输出: [1, 2, 3, 4, 5, 6]


参考：

https://www.cnblogs.com/ooo0/p/13091760.html