Java Collections - frequency() Method
The java.util.Collections.frequency() method returns the number of elements in the specified collection equal to the specified object.
Syntax
public static int frequency(Collection<?> c,
Object o)
Parameters
c |
Specify the collection in which to determine the frequency of o. |
o |
Specify the object whose frequency is to be determined. |
Return Value
Returns the number of elements in c equal to o.
Exception
Throws NullPointerException, if c is null.
Example:
In the example below, the java.util.Collections.frequency() method is used to find the number of occurrences of specified element in the given list.
import java.util.*;
public class MyClass {
public static void main(String[] args) {
//creating a list object
List<Integer> lst = new ArrayList<Integer>();
//populating lst
lst.add(10);
lst.add(10);
lst.add(30);
lst.add(10);
lst.add(20);
lst.add(30);
//printing the list
System.out.println("List contains: " + lst);
//printing the frequency of given element
System.out.print("Frequency of 10: ");
System.out.println(Collections.frequency(lst, 10));
System.out.print("Frequency of 20: ");
System.out.println(Collections.frequency(lst, 20));
System.out.print("Frequency of 30: ");
System.out.println(Collections.frequency(lst, 30));
}
}
The output of the above code will be:
List contains: [10, 10, 30, 10, 20, 30] Frequency of 10: 3 Frequency of 20: 1 Frequency of 30: 2
❮ Java.util - Collections
