Get unique values from arraylist in java

Question

I have an ArrayList with a number of records and one column contains gas names as CO2 CH4 SO2 etc.Now i want to retrieve different gas names(unique) only withou

Answer 1

You should use a Set. A Set is a Collection that contains no duplicates.

If you have a List that contains duplicates, you can get the unique entries like this:

List gasList = // create list with duplicates...
Set uniqueGas = new HashSet(gasList);
System.out.println("Unique gas count: " + uniqueGas.size());

NOTE: This HashSet constructor identifies duplicates by invoking the elements' equals() methods.