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POAdding a Generic allows you to override a method with a different return type?
 

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    <p>I ran into this today and the only thing I can think is that this is a bug in the Java compiler. The following code compiles, but certainly seems incorrect (since testMethod has a differenet signature in the child but overrides the parent) and will throw class cast exceptions at runtime.</p> <pre><code>public interface TestInterface&lt;T&gt; { public List&lt;String&gt; testMethod(); // &lt;-- List&lt;String&gt; } public class TestClass implements TestInterface { @Override public List&lt;Integer&gt; testMethod() { // &lt;-- List&lt;Integer&gt; overriding List&lt;String&gt;!! return Collections.singletonList(1); } } </code></pre> <p>And using the above structure:</p> <pre><code>public void test() { TestInterface&lt;Boolean&gt; test = new TestClass(); List&lt;String&gt; strings = test.testMethod(); for (String s : strings) { System.out.println(s); } } </code></pre> <p>All of this compiles fine, but will obviously throw class cast exceptions if you run it. </p> <p>If you remove <code>&lt;T&gt;</code> from <code>TestInterface</code>, or fill <code>T</code> in in the line <code>TestClass implements TestInterface&lt;T&gt;</code> then the code will no longer compile, which makes sense. Imo <code>&lt;T&gt;</code> should have no bearing on the compilation of <code>testMethod</code> since it plays no part in that method. Maybe adding <code>&lt;T&gt;</code> to TestInterface is causing the compiler to type-erase the method signatures even though <code>T</code> doesn't participate in those methods...?</p> <p>Does anyone know what is going on here?</p>
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    1. USMatt Crinklaw-Vogt
    1. USMatt Crinklaw-Vogt
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      1. USVictor Parmar
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    1. CO+1. Has to be some really, really strange gotcha in the generic implementation
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      1. USZach L
 

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