Remove duplicates (both values) - duplicate values from an ArrayList

In Java 8 you can do:

e.removeIf(s -> Collections.frequency(e, s) > 1);

If !Java 8 you can create a HashMap<String, Integer>. If the String already appears in the map, increment its key by one, otherwise, add it to the map.

For example:

put("123", 1);

Now let's assume that you have "123" again, you should get the count of the key and add one to it:

put("123", get("aaa") + 1);

Now you can easily iterate on the map and create a new array list with keys that their values are < 2.

References:

• ArrayList#removeIf
• Collections#frequency
• HashMap

You can also use filter in Java 8

e.stream().filter(s -> Collections.frequency(e, s) == 1).collect(Collectors.toList())