Pipeline design pattern implementation

why do you need an additional Pipeline class ? I think you can remove the middle man. this will make your api simpler, for example:

Step<Integer, String> source = Step.of(Object::toString);
Step<Integer, Integer> toHex = source.pipe(it -> Integer.parseInt(it, 16));

toHex.execute(11/*0x11*/);// return 17;

you can implement your pipeline pattern simply in java-8 as below :

interface Step<I, O> {

    O execute(I value);

    default <R> Step<I, R> pipe(Step<O, R> source) {
        return value -> source.execute(execute(value));
    }

    static <I, O> Step<I, O> of(Step<I, O> source) {
        return source;
    }
}

in prior java version you can use an abstract class instead:

abstract static class Step<I, O> {

    public abstract O execute(I value);

    public <R> Step<I, R> pipe(Step<O, R> source) {
        return new Step<I, R>() {
            @Override
            public R execute(I value) {
                return source.execute(Step.this.execute(value));
            }
        };
    }

    public static <I, O> Step<I, O> of(Step<I, O> source) {
        return source;
    }
}