Polymorphic uncurried method calls (adhoc polymorphism) in Java -

let me start example.

say have abstract vehicle class.

public abstract class vehicle {      public vehicle() {}      public abstract void ride();  } 

and classes car , bicycle inherit abstract class.

public class car extends vehicle {      public car() {}      @override     public void ride() {         system.out.println("riding car.");     }  }  public class bicycle extends vehicle {      public bicycle() {}      @override     public void ride() {         system.out.println("riding bicycle.");     }  } 

when apply ride() method object of type vehicle actual type can determined @ runtime, jvm apply correct version of ride().

that is, in curried method call of sort v.ride(), polymorphism works expected way.

but if have external implementation in form of method accepts subtype of vehicle argument? so, if have repair(bicycle b) , repair(car c) methods? uncurried polymorphic method call repair(v) won't work.

example:

import java.util.arraylist; import java.util.list;  public class main {  private static void playwithvehicle() {     list<vehicle> garage = new arraylist<vehicle>();     garage.add(new car());     garage.add(new car());     garage.add(new bicycle());     garage.foreach((v) -> v.ride()); // works.     garage.foreach((v) -> {         /* nice have.         repair(v.casttoruntimetype());         */          // ugly solution, obvious way can think of.         switch (v.getclass().getname()) {         case "bicycle":             repair((bicycle) v);             break;         case "car":             repair((car) v);             break;          default:             break;         }     }); }  private static void repair(bicycle b) {     system.out.println("repairing bicycle."); }  private static void repair(car c) {     system.out.println("repairing car."); }  public static void main(string[] args) {     playwithvehicle(); }  } 

i have check class name , downcast. there better solution this?

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edit: actual purpose i'm traversing abstract syntax tree , happened notice want double dispatch.

ast abstract class actual ast nodes assign, methodcall, or returnstmt inherit. body polymorphic list of asts.

code snippet:

list<ast> body;  body.parallelstream().foreach((ast) -> {     // 1 won't work.     visit(ast);     // 1 work.     if (ast instanceof assign) {         visit((assign) ast);     } else if (ast instance of methodcall) {         visit((methodcall) ast);     } else if (ast instance of returnstmt) {         visit((returnstmt) ast);     }     // etc. other ast nodes });  private void visit(assign ast) {  }  private void visit(methodcall ast) {  }  private void visit(returnstmt ast) {  } 

my possibilities of achieving double dispatch either checking class , downcasting or implementing visitor pattern, right?

answer: there no multiple dispatch in java , can simulated instanceof or visitor pattern.

see here: java method overloading + double dispatch

see here: https://en.wikipedia.org/wiki/multiple_dispatch#examples_of_emulating_multiple_dispatch

on sidenote, possible in c# dynamic calls: how build double dispatch using extensions

and possible in many languages compiled jvm bytecode, e.g. groovy mentioned.