Java 8 lambda stream

Question

I am trying to do the following but it throws error. Iterate over the list and call another method passing item as parameter and return true if it matches the condition.

I have below code:

public boolean myMethod() {
    List<String> list1 = method1();
    list1.forEach(item1 -> {
        List<String> list2 = method2(item1);
        if(list2.stream().anyMatch(item2 -> ***item2 condition***)) {
           return true;
        }
    });
    return false;
}

but return statement is not allowed inside for each. How can I achieve this?

Answer 1

Use another anyMatch to "bring the return value outside":

return list1.stream().anyMatch(item1 -> {
    List<String> list2 = method2(item1);
    return list2.stream().anyMatch(item2 -> item2 condition);
});

Or more simply, use a flatMap :

return list1.stream().flatMap(item1 -> method2(item1).stream()).anyMatch(item2 -> item2 condition);

Answer 2

You can use takeWhile

public static void main ( String [] args){
    System.out.println(check());
}

public static boolean check() {
    List<String> list1 = List.of("1", "2");
    var count = list1.stream().takeWhile(item1 -> {
        List<String> list2 = List.of("2", "3");
        return list2.stream().anyMatch(list2::contains);
    }).count();
    return count > 0;
}