Created
February 8, 2015 20:39
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Java destructuring visitor example
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abstract class Foo { | |
abstract <T> T match(Visitor<T> visitor); | |
interface Visitor<T> { | |
T caseManyBar(); | |
T caseBar(int i); | |
T caseBaz(String s); | |
} | |
static class Bar extends Foo { | |
private int bar; | |
private Bar(int bar) { | |
this.bar = bar; | |
} | |
@Override | |
<T> T match(Visitor<T> visitor) { | |
return bar > 10 ? visitor.caseManyBar() : visitor.caseBar(bar); | |
} | |
} | |
static class Baz extends Foo { | |
private String baz; | |
private Baz(String baz) { | |
this.baz = baz; | |
} | |
@Override | |
<T> T match(Visitor<T> visitor) { | |
return visitor.caseBaz(baz); | |
} | |
} | |
static void handle(Foo f) { | |
System.out.println(f.match(new Visitor<String>() { | |
@Override | |
public String caseBar(int i) { | |
return "I have " + i + " bars"; | |
} | |
@Override | |
public String caseManyBar() { | |
return "I have many bars"; | |
} | |
@Override | |
public String caseBaz(String s) { | |
return "I have the " + s + " baz"; | |
} | |
})); | |
} | |
public static void main(String[] args) { | |
handle(new Bar(42)); | |
handle(new Bar(3)); | |
handle(new Baz("Luhrmann")); | |
} | |
} |
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