Alwins Pattern Matchin Gist

AdtTest.java

import org.junit.Test;

public class AdtTest {

    @Test
    public void testStuff() {

        MyAdt adt = new MyBar();

        String result = adt.match(
                (foo) -> "do with foo",
                (bar) -> "do with bar"
        );

        System.out.println(result);
    }
}

MyAdt.java

import java.util.function.Consumer;

public interface MyAdt {

    interface MyAdtMatcher<R> {
        R with(MyFoo foo);
        R with(MyBar bar);
    }

    <R> R match(MyAdtMatcher<R> matcher);

    default <R> R match(Function<MyFoo, R> matchFoo, Function<MyBar, R> matchBar) {
        return match(new MyAdtMatcher<R>() {
            @Override
            public R with(MyFoo foo) {
                return matchFoo.apply(foo);
            }

            @Override
            public R with(MyBar bar) {
                return matchBar.apply(bar);
            }
        });
    }

    default void match(Consumer<MyFoo> matchFoo, Consumer<MyBar> matchBar) {
        match(new MyAdtMatcher<Void>() {
            @Override
            public Void with(MyFoo foo) {
                matchFoo.accept(foo);
                return null;
            }

            @Override
            public Void with(MyBar bar) {
                matchBar.accept(bar);
                return null;
            }
        });
    }

}

MyBar.java

public class MyBar implements MyAdt {
    @Override
    public void match(MyAdtMatcher matcher) {
        matcher.with(this);
    }
}

MyFoo.java

public class MyFoo implements MyAdt {

    @Override
    public void match(MyAdtMatcher matcher) {
        matcher.with(this);
    }
}