Lambda Expression is not working, getting terminated

Question

wrote java8 program with lambda expression, its not getting executed instead its getting terminated at the lambda expression, no exceptions

    import java.util.ArrayList;
    import java.util.List;
    import java.util.function.BiConsumer;

    public class BiConsumerTest {


    public static void main(String[] args) {
        try{


        List<String> list1 = new ArrayList<String>();

        list1.add("A");
        list1.add("B");
        list1.add("V");


    List<String> list2 = new ArrayList<String>();

        list2.add("J");
        list2.add("G");
        list2.add("P");

        BiConsumer<List<String>  , List<String>> bc = (lista, listb) ->{
                lista.stream().forEach( System.out::print);

            };


        }catch(Exception ex){
            ex.printStackTrace();
        }

    }

}

expected is it will print the string in list

Ousmane D. · Accepted Answer · 2019-01-02T12:00:22.390

3

This is because you're not calling the BiConsumer's accept method. call it as follows:

  bc.accept(list1, list2);

Further, note that it's not necessary to call stream just to call forEach instead call forEach directly on the list:

 lista.forEach(System.out::print);

Another thing is that your BiConsumer doesn't use the second list, this may be because you haven't finished implementing the entire logic yet in which case it's understandable.

Complete code:

BiConsumer<List<String>, List<String>> bc = (lista, listb) -> {
    lista.forEach(System.out::print);
    // listb.forEach(System.out::print);
};
bc.accept(list1, list2);

edited Jan 02 '19 at 12:00

answered Jan 02 '19 at 11:52

Ousmane D.

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Thanks for responding, could you please give me the entire syntax , I mean entire line with the code – user1245524 Jan 02 '19 at 11:59
for bc.accept(list1, list2); where should i call the lambda expression I am not getting – user1245524 Jan 02 '19 at 12:00
1

Thank you very much – user1245524 Jan 02 '19 at 12:39

Naman · Answer 2 · 2019-01-02T12:10:43.603

You've currently just defined the functional interface, to execute it further you need to invoke the implementation in your code. In your case, for this, you need to call the BiConsumer.accept method as:

bc.accept(list1, list2);

which then performs the operation, you've defined. As its Javadoc states

Performs this operation on the given arguments.

On another note, if I was to suggest, you might just be intending to print(at least) both the lists that you are consuming as :

BiConsumer<List<String>, List<String>> biConsumer = (lista, listb) -> {
    lista.forEach(System.out::print);
    listb.forEach(System.out::print);
};
biConsumer.accept(list1, list2);

which would print as an output A B V J G P.

(From comments) This could further be written as :

BiConsumer<List<String>, List<String>> biConsumer =
                      (lista, listb) -> Stream.concat(lista.stream(), listb.stream())
                                              .forEach( System.out::print);

`bc = (lista, listb) -> Stream.concat(lista.stream(),listb.stream()).forEach( System.out::print);` — Hadi J, Jan 02 '19 at 12:04
@HadiJ Well, agreed. Just that IMHO this question wasn't about the compute part. Thanks for the suggestion anyway. — Naman, Jan 02 '19 at 12:13

Lambda Expression is not working, getting terminated

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