javaforeachlambdajava-8

Break or return from Java 8 stream forEach?

When using external iteration over an Iterable we use break or return from enhanced for-each loop as:

for (SomeObject obj : someObjects) {
   if (some_condition_met) {
      break; // or return obj
   }
}

How can we break or return using the internal iteration in a Java 8 lambda expression like:

someObjects.forEach(obj -> {
   //what to do here?
})
Solution

  • If you need this, you shouldn't use forEach, but one of the other methods available on streams; which one, depends on what your goal is.

    For example, if the goal of this loop is to find the first element which matches some predicate:

    Optional<SomeObject> result =
    someObjects.stream().filter(obj -> some_condition_met).findFirst();

    (Note: This will not iterate the whole collection, because streams are lazily evaluated - it will stop at the first object that matches the condition).

    If you just want to know if there's an element in the collection for which the condition is true, you could use anyMatch:

    boolean result = someObjects.stream().anyMatch(obj -> some_condition_met);