Use Java 8 lambda expression...See https://github.com/java8/Java8InAction/blob/master/src/main/java/lambdasinaction/chap1/FilteringApples.java

FilteringApples.java

public class FilteringApples {

    public static List<Apple> filterGreenApple(List<Apple> inventory) {
        List<Apple> result = new ArrayList<>();
        for (Apple apple : inventory) {
            if ("green".equals(apple.getColor())) {
                result.add(apple);
            }
        }
        return result;
    }

    public static boolean isGreenApple(Apple apple) {
        return "green".equals(apple.getColor());
    }

    static List<Apple> filterApples(List<Apple> inventory, Predicate<Apple> p) {
        List<Apple> result = new ArrayList<>();
        for (Apple apple : inventory) {
            if (p.test(apple)) {
                result.add(apple);
            }
        }
        return result;
    }

    public static void main(String[] args) {

        List<Apple> inventory = Arrays.asList(new Apple(80, "green"),
                new Apple(155, "green"),
                new Apple(120, "red"));

        List<Apple> greenApples1 = filterGreenApple(inventory);
        List<Apple> greenApples2 = filterApples(inventory, FilteringApples::isGreenApple);
        List<Apple> greenApples3 = filterApples(inventory, (Apple a) -> "green".equals(a.getColor()));
        List<Apple> greenApples4 = inventory.stream().filter((Apple a) -> "green".equals(a.getColor()))
                                            .collect(Collectors.toList());
        List<Apple> greenApples5 = inventory.parallelStream().filter((Apple a) -> "green".equals(a.getColor()))
                                            .collect(Collectors.toList());
    }
    
    public static class Apple {
        ...
    }
}