Find Last Element Of A Stream

In this tutorial, here I am showing how to find the last element from a stream in java.

Note: we are using stream.reduce function for finding the last element of a stream in java. Stream.reduce method always returns Optional value, so you have to decide what to do when empty element is returned.

Find Last element of a Stream

The best way to get the last element of a stream is you can use stream().reduce method and below example you can see different versions of the method.

In case 1 you can see ‘D’ is returned and it is the last element of the stream. In case 2 there is no element in the stream and default element ‘E’ is returned. In case 3 there is no element in the stream and it is throwing an exception.

package com.javatips;

import java.util.Arrays;
import java.util.List;

public class GetStreamLastElment {

    public static void main(String[] args) {

	// case 1
	List<String> list = Arrays.asList("A", "B", "C", "D");
	list.stream().reduce((a, b) -> b).ifPresent(s -> System.out.println(s));

	// case 2
	list = Arrays.asList();
	System.out.println(list.stream().reduce((a, b) -> b).orElse("E"));

	// case 3
	list.stream().reduce((a, b) -> b).orElseThrow(() -> new IllegalStateException("no last element"));

    }

}

Output

D
E
Exception in thread "main" java.lang.IllegalStateException: no last element
	at com.javatips.GetStreamLastElment.lambda$4(GetStreamLastElment.java:16)
	at java.util.Optional.orElseThrow(Optional.java:290)
	at com.javatips.GetStreamLastElment.main(GetStreamLastElment.java:16)