Intersection and union of ArrayLists in Java

Question

Are there any methods to do so? I was looking but couldn\'t find any.

Another question: I need these methods so I can filter files. Some are AND filter

Answer 1

Collection (so ArrayList also) have:

col.retainAll(otherCol) // for intersection
col.addAll(otherCol) // for union

Use a List implementation if you accept repetitions, a Set implementation if you don't:

Collection col1 = new ArrayList(); // {a, b, c}
// Collection col1 = new TreeSet();
col1.add("a");
col1.add("b");
col1.add("c");

Collection col2 = new ArrayList(); // {b, c, d, e}
// Collection col2 = new TreeSet();
col2.add("b");
col2.add("c");
col2.add("d");
col2.add("e");

col1.addAll(col2);
System.out.println(col1); 
//output for ArrayList: [a, b, c, b, c, d, e]
//output for TreeSet: [a, b, c, d, e]