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I find it weird and was wondering if it is something that is regularly used. When can it be useful?
public interface InterA {
Object getInfo() throws Exception1;
}
public interface InterB {
public default Integer getInfo(Object s) {return 67;}
}
public interface InterC extends InterA, InterB {
@Override public abstract Integer getInfo(Object s);
}
648
A default method cannot override a method from java.
An abstract class can override Object class methods, but an interface can't. An abstract class can declare instance variables, with all possible access modifiers, and they can be accessed in child classes. An interface can only have public, static, and final variables and can't have any instance variables.
An abstract class permits you to make functionality that subclasses can implement or override whereas an interface only permits you to state functionality but not to implement it. A class can extend only one abstract class while a class can implement multiple interfaces.
It is not mandatory to override the default method in Java.
This exists before default interface methods. For example, an abstract class can make
@Override
abstract public int hashCode();
forcing subclasses to provide implementations for hashCode, possibly because of additional requirements imposed by the abstract class.
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