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up vote 3 down vote favorite

Basically something like

public void jumpToRoom(String roomName = Rooms.DEFAULT_ROOM)

would be convenient.

Many languages nowadays seem to support it (Ruby, PHP, even C#).

What is Java's reasoning for not allowing it?

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Key things - look at the timeframe that the java spec was written and the languages that could influence to have default parameters (Java class libs where developed 4 years prior to Ruby or PHP showing up). Going into the "reasoning for not allowing it?", unless one can find a document by Gosling saying one way or the other nearly any answer will be speculation. – MichaelT Jan 15 at 20:05
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@MichaelT Java was extended since then though, and C# successfully added default parameters atop of an even larger language. – delnan Jan 15 at 20:12
@MichaelT: Default argument values weren't invented by Ruby or PHP. FORTRAN had optional arguments, and C++ had default arguments a decade prior to Java. The latter had a very heavy influence on the design of Oak, which was intended to be a better C++. Oak eventually morphed into Java. – Blrfl Jan 15 at 20:19

closed as not constructive by ChrisF♦ Jan 15 at 20:49

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1 Answer

up vote 3 down vote

One good reason is to simplify overloading. For example if void foo(String a); and void foo(String a,String b default: "bar")

both exist what does foo("bar") call?

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Neither, it generates a compiler error. Possibly already at one of the two definitions. – delnan Jan 15 at 20:11
C# supports overloading and optional arguments – K2xL Jan 15 at 20:22
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To be more specific, C# has sensible rules for overload resolution when optional arguments are employed. Generally speaking, the most specific overload match wins. – Robert Harvey Jan 15 at 20:23
"both exist what does foo("bar") call?": You can define proper rules to resolve the ambiguity but it makes the language's semantics more complex. Java tends to favour minimalism. – Giorgio Apr 2 at 10:58
I would hope it wouldn't generate a compiler error because that may break backward compatibility. – Brandon May 10 at 12:29

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