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In Java, all methods are virtual. You can often achieve a similar effect to non-virtual methods by declaring them final to prevent them being overridden in subc

by army 13y ago

In Java, all methods are virtual. You can often achieve a similar effect to non-virtual methods by declaring them final to prevent them being overridden in subclasses, but the same rules about which method is called apply. The reason to simplify the language (in comparison to C++) - the rules about which method are called are much simpler and easy to remember.

MichaelGG 13y ago
Simpler? The only case it matters is when a subclass has shadowed a non-virtual method. "Simpler" would be simply disallowing shadowing.
- AndrewBissell 13y ago
  Not having to think about the question "should I make this method virtual?" makes the Java language simpler, yes. In the vast majority of cases where a virtual function call is actually monomorphic or bimorphic at runtime, the JVM JIT can observe that and potentially inline the method (with an if statement in the bimorphic case). It puts guards around the inlined method and deoptimizes in the event that a newly loaded class renders the optimization incorrect.
  - MichaelGG 13y ago
    It just flips it for "should I make this method final?" So at best it's a wash. In the majority of cases, a function shouldn't be virtual so users need to mark it final to accurately represent their design.
    - AndrewBissell 13y ago
      Well, the answer to "should I make x final" is always "yes" in Java, so you don't really have to think too hard about that either. :-) `final` really should have been the default setting for all methods, classes, and local variables, but unfortunately inheritance was still in vogue when Java was created, and the benefits of immutable values weren't as well understood or appreciated either (or maybe they just figured the C & C++ programmers they were trying to win over would hate it).
kasey_junk 13y ago
Also depending on the JVM and JIT settings over time those virtual methods get treated as non-virtual.

by army 13y ago

MichaelGG 13y ago

Simpler? The only case it matters is when a subclass has shadowed a non-virtual method. "Simpler" would be simply disallowing shadowing.

AndrewBissell 13y ago
Not having to think about the question "should I make this method virtual?" makes the Java language simpler, yes. In the vast majority of cases where a virtual function call is actually monomorphic or bimorphic at runtime, the JVM JIT can observe that and potentially inline the method (with an if statement in the bimorphic case). It puts guards around the inlined method and deoptimizes in the event that a newly loaded class renders the optimization incorrect.
- MichaelGG 13y ago
  It just flips it for "should I make this method final?" So at best it's a wash. In the majority of cases, a function shouldn't be virtual so users need to mark it final to accurately represent their design.
  - AndrewBissell 13y ago
    Well, the answer to "should I make x final" is always "yes" in Java, so you don't really have to think too hard about that either. :-) `final` really should have been the default setting for all methods, classes, and local variables, but unfortunately inheritance was still in vogue when Java was created, and the benefits of immutable values weren't as well understood or appreciated either (or maybe they just figured the C & C++ programmers they were trying to win over would hate it).

kasey_junk 13y ago

Also depending on the JVM and JIT settings over time those virtual methods get treated as non-virtual.