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kevinpet/Foo.java

Created February 8, 2015 21:51
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Revisions

  1. kevinpet created this gist Feb 8, 2015.
    52 changes: 52 additions & 0 deletions Foo.java
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,52 @@
    abstract class Foo {
    abstract <T> T match(Visitor<T> visitor);

    interface Visitor<T> {
    T caseBar(Bar b);
    T caseBaz(Baz b);
    }

    static class Bar extends Foo {
    final int bar;

    private Bar(int bar) {
    this.bar = bar;
    }

    @Override
    <T> T match(Visitor<T> visitor) {
    return visitor.caseBar(this);
    }
    }

    static class Baz extends Foo {
    final String baz;

    private Baz(String baz) {
    this.baz = baz;
    }

    @Override
    <T> T match(Visitor<T> visitor) {
    return visitor.caseBaz(this);
    }
    }

    static void handle(Foo f) {
    System.out.println(f.match(new Visitor<String>() {
    @Override
    public String caseBar(Bar b) {
    return "I have " + b.bar + " bars";
    }
    @Override
    public String caseBaz(Baz b) {
    return "I have the " + b.baz + " baz";
    }
    }));
    }

    public static void main(String[] args) {
    handle(new Bar(42));
    handle(new Baz("Luhrmann"));
    }
    }