Performance issue while iterating with streams

srikotesh
srikotesh used Ask the Experts™
on
Hi Experts,

I have written the below program using java7 and java8

Collections are giving me result quickly when i compared with streams
Is any thing wrong in my code.
can some one suggest me what exactly the issue with streams iteration.

Collections is taking only 16 milliseconds
FROM STREAMS
localCaloricDishesName  [EggCurry, BeatRootCurry, LadyFinger]
109 millis

package com.java8;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

public class StreamAndFilter  {

	public static void main1(String[] args) {
		Long startTime = System.currentTimeMillis();	
		List<Dish> menu = new ArrayList<>();
		menu.add(new Dish("CarrotCurry",405));
		menu.add(new Dish("BeatRootCurry",215));
		menu.add(new Dish("PotatosCurry",450));
		menu.add(new Dish("TamatoCurry",500));
		menu.add(new Dish("LadyFinger",300));
		menu.add(new Dish("EggCurry",200));
		
		List<Dish> localCaloricDishesName = new ArrayList<>();
		
		for (Dish dish : menu) {
			if(dish.getCalories()<400){
				localCaloricDishesName.add(dish);
			}
		}
		
		Collections.sort(localCaloricDishesName,new Comparator<Dish>() {

			@Override
			public int compare(Dish o1, Dish o2) {
				// TODO Auto-generated method stub
				return Integer.compare(o1.getCalories(), o2.getCalories());
			}
			
		});
		
		List<String> curryNames = new ArrayList<String>();
		for (Dish dish : localCaloricDishesName) {
			curryNames.add(dish.getDishName());
		}
		
		System.out.println("curryNames"+curryNames);;
		System.out.println(System.currentTimeMillis()-startTime);
	}
	
	public static void main(String[] args) {
		System.out.println("FROM STREAMS");
		Long startTime = System.currentTimeMillis();
		List<Dish> menu = new ArrayList<>();
		menu.add(new Dish("CarrotCurry",405));
		menu.add(new Dish("BeatRootCurry",215));
		menu.add(new Dish("PotatosCurry",450));
		menu.add(new Dish("TamatoCurry",500));
		menu.add(new Dish("LadyFinger",300));
		menu.add(new Dish("EggCurry",200));
		
		List<String> localCaloricDishesName = 
				menu.stream()
				.filter(d->d.getCalories()<400)
				.sorted(Comparator.comparing(Dish :: getCalories))
				.map(Dish::getDishName)
				.collect(Collectors.toList());
		
		System.out.println("localCaloricDishesName  "+localCaloricDishesName);
		System.out.println(System.currentTimeMillis()-startTime);		
	}
}

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Senior Java Architect
Commented:
I don't see anything obviously wrong with your code; streams just have higher processing overhead than enhanced for loops. The difference is probably smaller when you're dealing with larger collections. Streams would definitely use less memory, when processing large collections, because you're not making so many intermediate collections along the way.

Author

Commented:
Hi CPColin,

IF possible can you show me a sample example which improves performance.
CPColinSenior Java Architect

Commented:
Nope. To reiterate what I said in my last comment: Your code is fine; streams just have more overhead.

Author

Commented:
Memory wise streams are better than collection
Performance wise stream slower than collection
AM I correct?
CPColinSenior Java Architect

Commented:
It depends entirely on what you're doing. My standard advice is that you should focus on writing code that clearly shows your intent and worry about performance if and when it becomes a problem.

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