Efficient intersection of two List in Java?

Question

Question is simple:

I have two List

List columnsOld = DBUtils.GetColumns(db, TableName);
List columnsNew = DBUtils.GetCol         


        

Answer 1

using retainAll if don't care occurrences, otherwise using N.intersection

a = N.asList(12, 16, 16, 17, 19);
b = N.asList(16, 19, 107);
a.retainAll(b); // [16, 16, 19]
N.println(a);

a = N.asList(12, 16, 16, 17, 19);
b = N.asList(16, 19, 107);
a = N.intersect(a, b);
N.println(a); // [16, 19]

N is an utility class in AbacusUtil