Question

Is there an equivalent of python’s itertools.chain for Java (with third-party libraries or without)?

itertools.chain([1, 2, 3], [4, 5, 6]) # -> [1, 2, 3, 4, 5, 6]

Something like this:

new Iterable<E> {
       public Iterator<E> iterator() {
           return new Iterator<E>() {
               Iterator<E> i1 = list1.iterator();
               Iterator<E> i2 = list2.iterator();
               public boolean hasNext() {
                   return i1.hasNext() || i2.hasNext();
               }
               public E next() {
                   if(i1.hasNext()) {
                       return i1.next();
                   } else if(i2.hasNext()) {
                       return i2.next();
                   } else {
                       throw new NoSuchElementException("Lists exhausted");
                   }
               }
               public void remove() {
                   throw new UnsupportedOperationException("...");
               }
           }
       }
   }

Answer 1

There is: com.google.common.collect.Iterables#concat()