This is not a duplicate of my question. I checked it and mine is how to use proper Predicate, and THAT is about differences between removeIf & remove.
I'm beginner Java programmer.
Yesterday, I tried to follow this tutorial https://dzone.com/articles/why-we-need-lambda-expressions
After I leared how to use Lambda expressions and Predicate, I made my own code to practice.
like, sum all numbers if(n % 3 == 0 || n % 5 == 0). here is my code.
public class Euler1Lambda { long max; public Euler1Lambda(long max) { this.max = max; } public static boolean div3remainder0(int number) { return number % 3 == 0; } public static boolean div5remainder0(int number) { return number % 5 == 0; } public long sumAll() { long sum = 0; for(int i=1; i<max; i++) { if (div3remainder0(i) ||div5remainder0(i)) { sum += i; } } return sum; } public long sumAllLambda(Predicate<Integer> p) { long total = 0; for (int i = 1; i< max; i++){ if (p.test(i)) { total += i; } } return total; } public static void main(String[] args) { //conv long startTime = System.currentTimeMillis(); for(int i = 0; i < 10; i++){ new Euler1Lambda(100000000).sumAll(); } long endTime = System.currentTimeMillis(); long conv = (endTime - startTime); System.out.println("Total execution time: " + conv); //lambda startTime = System.currentTimeMillis(); for(int i = 0; i < 10; i++){ new Euler1Lambda(100000000).sumAllLambda(n -> div3remainder0(n) || div5remainder0(n)); } endTime = System.currentTimeMillis(); long lambda = (endTime - startTime); System.out.println("Total execution time: " + lambda); System.out.println("lambda / conv : " + (float)lambda/conv); } } In this code, did timing tests. and result is like this.
Total execution time conv: 1761 Total execution time lambda: 3266 lambda / conv : 1.8546281 As you can see, lambda expression with predicate is slower than simple for-loop.
I have no idea why does the result like this.
What am I doing wrong? or just predicate is too slow way to use?
