gistfile1.txt

package org.drools.java8;

import java.util.*;

public class Java8Example {

    Rule rule1 = new Rule()
            .when( (Person person) -> person.getAge() >= 18 )
                    .and( (Person person, Pet pet) -> pet.getOwner() == person )
            .then( (Person person, Pet pet) -> System.out.println("Person" + person + "is the owner of" + pet) );

    public static interface Tuple { }

    public static interface CTuple1<E1> extends Tuple {
        boolean invoke(E1 t);
    }

    public static interface CTuple2<E1, E2> extends Tuple {
        boolean invoke(E1 e1, E2 e2);
    }

    public static interface CTuple3<E1, E2, E3> extends Tuple {
        boolean invoke(E1 e1, E2 e2, E3 e3);
    }


    public static interface ATuple1<E1> extends Tuple {
        void invoke(E1 t);
    }

    public static interface ATuple2<E1, E2> extends Tuple{
        void invoke(E1 e1, E2 e2);
    }

    public static interface ATuple3<E1, E2, E3> extends Tuple {
        void invoke(E1 e1, E2 e2, E3 e3);
    }


    public static class Rule {

        private Condition when;
        private Tuple then;

        public Rule() {}

        public Condition when(CTuple1<?> then) {
            return when = new Condition(this, then);
        }

        public Condition when(CTuple2<?,?> then) {
            return when = new Condition(this, then);
        }

        public Condition when(CTuple3<?,?,?> then) {
            return when = new Condition(this, then);
        }

        public Rule then(ATuple1<?> then) {
            this.then = then;
            return this;
        }

        public Rule then(ATuple2<?,?> then) {
            this.then = then;
            return this;
        }

        public Rule then(ATuple3<?,?,?> then) {
            this.then = then;
            return this;
        }
    }

    public static class Condition {
        private final Rule rule;
        private List<Tuple> when = new ArrayList<Tuple>();

        public Condition(Rule rule, Tuple then) {
            this.rule = rule;
            when.add(then);
        }

        public Condition and(CTuple1<?> then) {
            when.add(then);
            return this;
        }

        public Condition and(CTuple2<?,?> then) {
            when.add(then);
            return this;
        }

        public Condition and(CTuple3<?,?,?> then) {
            when.add(then);
            return this;
        }

        public Rule then(ATuple1<?> then) {
            return rule.then(then);
        }

        public Rule then(ATuple2<?,?> then) {
            return rule.then(then);
        }

        public Rule then(ATuple3<?,?,?> then) {
            return rule.then(then);
        }
    }



    public static class Person {
        private String name;
        private int age;
        public Person(String name, int age) {
            this.name = name;
            this.age = age;
        }

        public int getAge() {
            return age;
        }
    }

    public static class Pet {
        private String name;
        private Person owner;
        private String type;

        public Pet(String name, Person owner, String type) {
            this.name = name;
            this.owner = owner;
            this.type = type;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public Person getOwner() {
            return owner;
        }

        public void setOwner(Person owner) {
            this.owner = owner;
        }

        public String getType() {
            return type;
        }

        public void setType(String type) {
            this.type = type;
        }
    }

    public static class Location {
        private String person;
        private String place;

        public Location(String person, String place) {
            this.person = person;
            this.place = place;
        }

        public String getPerson() {
            return person;
        }

        public void setPerson(String person) {
            this.person = person;
        }

        public String getPlace() {
            return place;
        }

        public void setPlace(String place) {
            this.place = place;
        }
    }


}