Discovery which itens are not duplicated

LessPerformanceApproach.java

package com.moogu.restore;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class LessPerformanceApproach {

	public static void main(String[] args) {
		List<String> letters = Arrays.asList("a", "b", "c", "d", "e", "f", "g", "f", "e", "c", "b");
		LessPerformanceApproach main = new LessPerformanceApproach();
		System.out.println(main.processStream(letters.stream()));
	}

	private List<String> processStream(Stream<String> stream) {
		List<String> result = new ArrayList<>();
		List<String> allValues = stream.collect(Collectors.toList());
		for (String value : allValues) {
			if (Collections.frequency(allValues, value) == 1) {
				result.add(value);
			}
		}
		return result;
	}
}