Before Java 8, lambda functionality could be achieved by using anonymous inner classes. For example:
interface Lambda { void doStuff(); } // ... public void doWithCallback(Lambda callback) { // ... callback.doStuff(); } // ... doWithCallback(new Lambda { public void doStuff() { // ... } }); In terms of performance, is there a difference between still using this approach and using the new Java 8 lambdas?
Oracle has posted a study comparing performance between Lambdas and anonymous classes
See JDK 8: Lambda Performance Study by Sergey Kuksenko, which is 74 slides long.
Summary: slow to warm up but when JIT inlines it worst case just as fast as anonymous class but can be faster.
As I found, the iterating over array with Stream is working much slower (74 slides are not consider such the case). I think that it is not the only performance leaks in lambdas (guess, it will be improved in the future). The example below was running with Java 8 without any options:
//Language is an enum Language[] array = Language.values(); System.err.println(array.length); // 72 items long t = System.nanoTime(); for (Language l : array) System.out.println(l.getLanguageName()); System.err.println(System.nanoTime()-t); //nano time 1864724 t = System.nanoTime(); Arrays.stream(array).forEach(v -> System.out.println(v.getLanguageName())); System.err.println(System.nanoTime()-t); //nano time 55812625 (55812625/1864724 = 29.93 times longer) List list = Arrays.asList(array); t = System.nanoTime(); for (Language l : list) System.out.println(l.getLanguageName()); System.err.println(System.nanoTime()-t); //nano time 1435008 t = System.nanoTime(); list.forEach(v -> System.out.println(v.getLanguageName())); System.err.println(System.nanoTime()-t); //nano time 1619973 (1619973/1435008 = 1.128 times longer)