UTP ćwiczenia

package Zad4;

import java.util.NoSuchElementException;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;

public class Maybe<T> {

    private T value;

    private boolean present;

    private Maybe(T value) {
        present = true;
        this.value = value;
    }

    private Maybe() {
        present = false;
    }

    public static <T> Maybe<T> of(T value) {
        if (value == null)
            return new Maybe<>();
        else
            return new Maybe<>(value);

    }

    public void ifPresent(Consumer<T> cons) {
        if (present)
            cons.accept(value);
    }


    public <T, S> Maybe <T> map (Function <T, S> func){
            return Maybe.of(func.apply(value));
    }

    public T get (){
        if(present)
            return value;
        else
            throw new NoSuchElementException("maybe is empty");
    }

    public boolean isPresent(){
        return present;
    }

    public <T> T orElse(T defVal){
        if(present)
            return (T)value;
        else
            return defVal;
    }

    public <T> Maybe filter(Predicate<T> pred){
        if(pred.test((T) this.value))
            return this;
        else
            return new Maybe();
    }
}