How to check if exists any duplicate in Java 8 Streams?

Question

In java 8, what\'s the best way to check if a List contains any duplicate?

My idea was something like:

list.size() != list.stream().distinct().count(         


        

Answer 1

Started this class as a StreamTool, but I think there must be an even better way with reduce or similar:

public class StreamTool {

    /**
     * Whether stream records are unique in that stream.
     * @param  Type of records
     * @param records
     * @return true if there are no duplicates, false otherwise
     */
    public static  boolean isUnique(Stream records) {
        return records.allMatch(new HashSet<>()::add);
    }
}