Java 8 Streams - How to find the duplicate elements from a Collection - Multiple ways
Example 1: Using Collections.frequency() To find frequency of a particular element we can use the frequency() method: import java.util.Arrays; import java.util.Collections; import java.util.List; import java.util.stream.Collectors; public class DriverClass { public static void main( String [] args) { List < String > obj = Arrays.asList( "ant" , "1" , "cat" , "ant" , "we" , "java" , "cat" ); obj.stream().filter(i -> Collections. frequency(obj, i) > 1 ).collect(Collectors.toSet()) .forEach(System.out :: println); } } Output: ant cat Example 2: Using Collectors.groupingBy() We can also use the Collectors.groupingBy() method to count the frequency of elements present in a stream. import java.util.Arrays; import java.util.List; import java.util.Map; import java.util.Set; import java.util.function.Function; import java