package blatt14;

public class List<T> {

    private final T info;
    private final List<T> next;

    public List(T info, List<T> next) {
        this.info = info;
        this.next = next;
    }

    public static <S> List<S> filter(List<S> node, Predicate<S> pred) {
        if (node == null)
            return null;
        
        List<S> rest = filter(node.next, pred);
        
        if (pred.applies(node.info) == true) {
            return new List<>(node.info, rest);
        } else {
            return rest;
        }
    }
    
    
    public static <S> List<S> filter2(List<S> node, Predicate<S> pred) {
        List<S> ret = null;
        
        while (node != null) {
            if (pred.applies(node.info)) {
                ret = new List<S>(node.info, ret);
            }
            
            node = node.next;
        }
        
        return ret;
    }
}

interface Predicate<T> {
    boolean applies(T toWhat);
}