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Prevent anonymously subclassing
Is it possible to somehow prohibit anonymously subclassing of a specific class? For instance, with a plain public parent class:
public class Parent {
}
Extending this class should not be possible with an unnamed, anonymous subclass:
var myClass = new Parent() { ... }
However, all other forms of subclassing or usage should work, such as:
public class Child extends Parent {
public static Object feelingLucky(boolean really) {
return really ? new Child() : new Parent();
}
}
1 answer
There is no keyword or compile-time construct to prevent this, but it can be accomplished through the use of a runtime exception:
class Parent {
public Parent() {
if (getClass().isAnonymousClass()) {
throw new IllegalStateException("You violated my secret rule!");
}
}
}
For actual use in production code, one should probably reconsider the reasons for which one would like to do this. Limiting the creation of anonymous classes is a possibility, but generally a bad idea.
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