M Sach M Sach - 9 months ago 36
Java Question

Why lambda expression in java?

I understand with lambda expression(LE) we can save few lines of coding like object creation for functional interface. Also LE will be more readable. But i am sure that this is not the main reason this feature is provided for. I search it on google for

Why Lambda expression in java
and i found this interesting quote at this article

Prior to Java 8, processing the elements of any collection could be
done by obtaining an iterator from the collection and then iterating
over the elements and then processing each element. If the requirement
is to process the elements in parallel, it would be done by the client
code. With the introduction of Stream API in Java 8, functions can be
passed to collection methods and now it is the responsibility of
collection to process the elements either in a sequential or parallel
manner. -

To me this looks like the advantage of streaming api not LE. Even if LE was not provided developer could have achieved the same
with creation of anonymous Consumer class. The only advantage here i can see in favour of LE is developer does not have to remember object of which
functional interface needs to be created. So it takes java towards functional programming where dev is saying apply this function and he does not care
about object(let jvm handle this).

Is this the main advantage of LE or there is another one major than this ?

Update :-

I tried below simple program where i tried to measure the performance parallel processing with lambda expression. Found that it took 84 unit of time with parallel processing and only 4 unit for sequential. Is it because program is not big enough and also thread overhead may be playing its role here ? May be advantages can be visible in larger function ?

public class Java8Tester {

final static String salutation = "Hello! ";

public static void main(String args[]){
List<String> stringList = new ArrayList<String>();

for(int i=0;i <100;i++){

long startTime = System.currentTimeMillis();
stringList.parallelStream().forEach((string) -> {System.out.println("content is " + string);
long stopTime = System.currentTimeMillis();
System.out.println("time taken in parallel processing" + (stopTime - startTime)); // took 84 units of time

startTime = System.currentTimeMillis();

for(String str : stringList ) {
System.out.println("content is " + str);

stopTime = System.currentTimeMillis();
System.out.println("time taken in sequential processing" + (stopTime - startTime)); // // took 4 units of time


Answer Source

In general you're right: Stream API could exist without lambda functions, using anonymous classes. Though it would look really ugly and work somewhat less efficiently. As for time measurement, your results are completely irrelevant. See this question for details.