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POHow do I make the method return type generic?
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  1. POHow do I make the method return type generic?
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    copied!<p>Consider this example (typical in OOP books): </p> <p>I have an <code>Animal</code> class, where each <code>Animal</code> can have many friends.<br> And subclasses like <code>Dog</code>, <code>Duck</code>, <code>Mouse</code> etc which add specific behavior like <code>bark()</code>, <code>quack()</code> etc.</p> <p>Here's the <code>Animal</code> class:</p> <pre><code>public class Animal { private Map&lt;String,Animal&gt; friends = new HashMap&lt;&gt;(); public void addFriend(String name, Animal animal){ friends.put(name,animal); } public Animal callFriend(String name){ return friends.get(name); } } </code></pre> <p>And here's some code snippet with lots of typecasting:</p> <pre><code>Mouse jerry = new Mouse(); jerry.addFriend("spike", new Dog()); jerry.addFriend("quacker", new Duck()); ((Dog) jerry.callFriend("spike")).bark(); ((Duck) jerry.callFriend("quacker")).quack(); </code></pre> <p>Is there any way I can use generics for the return type to get rid of the typecasting, so that I can say </p> <pre><code>jerry.callFriend("spike").bark(); jerry.callFriend("quacker").quack(); </code></pre> <p>Here's some initial code with return type conveyed to the method as a parameter that's never used. </p> <pre><code>public&lt;T extends Animal&gt; T callFriend(String name, T unusedTypeObj){ return (T)friends.get(name); } </code></pre> <p>Is there a way to figure out the return type at runtime without the extra parameter using <code>instanceof</code>? Or at least by passing a class of the type instead of a dummy instance.<br> I understand generics are for compile time type-checking, but is there a workaround for this?</p>
 

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