In java8, how to set the global value in the lambdas foreach block?

You could, of course, “make the outer value mutable” via a trick:

public void test() {
    String[] x = new String[1];
    List<String> list = Arrays.asList("a", "b", "c", "d");

    list.forEach(n -> {
        if (n.equals("d"))
            x[0] = "match the value";
    });
}

Get ready for a beating by the functional purist on the team, though. Much nicer, however, is to use a more functional approach (similar to Sleiman’s approach):

public void test() {
    List<String> list = Arrays.asList("a", "b", "c", "d");
    String x = list.stream()
                   .filter("d"::equals)
                   .findAny()
                   .map(v -> "match the value")
                   .orElse(null);
}