java streams supposed to be better performance, but my test says otherwise.

[Warren Goldman]

The test case shows streams approach to filter then sort is much slower on first call, seems to speed up on second and third, but the old way of sorting and filtering seems to be quicker.

Can anyone explain this?

Here are the results:
new:49 count: 2500
old:4 count: 2500
new:2 count: 2500
old:2 count: 2500
new:1 count: 2500

Files with the extension .java are not allowed as attachment in the message... so here is the code...

public class Test {
	public static void main(String[] args) {
		Test t = new Test();
		t.run();
	}

	public void run() {
		java.util.List<Apple> allApples = createAllAppleList();
		java.util.List<Apple> allApples2 = createAllAppleList();
		checkNewWay(allApples2);
		checkOldWay(allApples);
		checkNewWay(allApples);
		checkOldWay(allApples);
		checkNewWay(allApples);
	}

	private void checkNewWay(java.util.List<Apple> allApples) {
		long newStartTime = System.currentTimeMillis();
		java.util.List newRedsSorted = allApples.stream()
			.filter(apple -> apple.getColor().equals("red"))
			.sorted((firstApple, secondApple) -> firstApple.getSweetness().compareTo(secondApple.getSweetness()))
			.collect(java.util.stream.Collectors.toList());
		long newEndTime = System.currentTimeMillis();
		long newTimeElapsed = newEndTime - newStartTime;
		System.out.println("new:" + newTimeElapsed + " count: " + newRedsSorted.size());
		runCheck(newRedsSorted);
	}
	private void checkOldWay(java.util.List<Apple> allApples) {
		long startTime = System.currentTimeMillis();
		java.util.Comparator<Apple> comparator = new java.util.Comparator<Apple>() {
			public int compare(Apple firstApple, Apple secondApple) {
				return firstApple.getSweetness().compareTo(secondApple.getSweetness());
			}
		};
		java.util.List<Apple> redApplesSorted = new java.util.ArrayList<Apple>();
		for (Apple apple:allApples) {
			if (apple.getColor().equals("red")) {
				redApplesSorted.add(apple);
			}
		}
		java.util.Collections.sort(redApplesSorted, comparator);
		long endTime = System.currentTimeMillis();

		long oldTimeElapsed = endTime - startTime;
		System.out.println("old:" + oldTimeElapsed + " count: " + redApplesSorted.size());
		runCheck(redApplesSorted);
	}

	private java.util.List<Apple> createAllAppleList() {
		java.util.ArrayList<Apple> list = new java.util.ArrayList<Apple>();
		java.util.Random r = new java.util.Random();
		for (int i = 0; i< 10000; i++) {
			Apple apple = new Apple();
			if (i % 4 == 0) {
				apple.setColor("red");
			} else if (i % 3 == 0) {
				apple.setColor("green");
			} else {
				apple.setColor("yellow");
			}
			apple.setSweetness(getSweetness(r));
			apple.setType(apple.getColor() + ":" + apple.getSweetness());
			list.add(apple);
		}
		return list;
	}

	private void runCheck(java.util.List<Apple> apps) {
		int currentSweetness = -44;
		for (Apple apple:apps) {
			if (currentSweetness >= apple.getSweetness()) {
				System.out.println("***** FAILED***** current:" + currentSweetness + ", apples:" + apple.getSweetness());
				break;
			}
			currentSweetness = apple.getSweetness();
			if (!apple.getColor().equals("red")) {
				System.out.println("wrong color");
			}
		}
	}

	private int getSweetness(java.util.Random r) {
		int nbr = r.nextInt();
		if (nbr < 1) {
			nbr = getSweetness(r);
		}
		return nbr;
	}

	public static class Apple {
		private String color;

		private Integer sweetness;
		 
		private String type;

		public String getColor() {
		    return color;
		}
		 
		public void setColor(String color) {
		    this.color = color;
		}
		 
		public Integer getSweetness() {
		    return sweetness;
		}
		 
		public void setSweetness(Integer sweetness) {
		    this.sweetness = sweetness;
		}

		public String getType() {
		    return type;
		}
		 
		public void setType(String type) {
		    this.type = type;
		}
	}
}

[Campbell Ritchie]

I suspect the acceleration on subsequent runs may be caused by just in time compilation.

[Campbell Ritchie]

… but my suspicion may be incorrect.

[Paweł Baczyński]

Warren Goldman wrote:Files with the extension .java are not allowed as attachment in the message... so here is the code...

Actually you should put your code inside [code] tags like you just did.
You can read more about those here: UseCodeTags (click)

[Rahul Mahindrakar]

Hi

The only thing I can see is that the lack of usage of parallelStream()

--
java.util.List newRedsSorted = allApples.parallelStream()
--

But when I changed it still no change in result.

Intresting problem!

[Mohamed Sanaulla]

This discussion should be of help where a similar experiment of using Collections API and Stream API was used for sorting of Integers.