Re: java.util.Properties extending from HashMap<Object, Object> instead of HashMap<String, String>

Zig wrote:
If this method existed, and you were tasked with calling this method such as:

Integer version=(Integer) createProps().get("version");

This code would likely not compile in Java 5 if properties was made as Hashtable<String,String>...

As I was thinking about this, it seems I may have been in error. In theory, a crafty developer could call:

Map<String,String> props=createProps();
Integer version=(Integer) ((Map<String, ?>) props).get("version");

That's nice and obfuscated, but in theory one could still get data out of a hypothetical Properties<String,String>, which was used for non-string values in a 3rd party 1.4 API.

I guess the answer might be that, when one implements Map<String,String>, methods expect to iterate over map.getEntrySet() as Map.Entry<String,String> without worrying about class cast exceptions. It is the Java 5 developer's job to create a Hashtable<String, Object>, when they need to pass a Hashtable to a Java 1.4 method that uses non-string values.

So perhaps for properties, a type was chosen, so users would not have to specify it at every use, avoiding things like

Properties<String,String> props=new Properties<String,String>()

but, users iterating over values should still be aware that legacy APIs could have used properties for things besides String, and developers would need to make a decision on when to use getProperty(String) vs get(Object).

Anyway, that's my current best guess. Any takers?

Completely wrong. Properties is meant for Strings only. It is not intended for use as a Map at all, really.

--
Lew
.

Relevant Pages

  • Re: Help me!! Why java is so popular
    ... String or StringBuffer? ... keep in mind I knew NOTHING about Java. ... The language accepted it, no warnings, and thus I ... in some native assemblers you can peruse the instruction ...
    (comp.lang.java.programmer)
  • Re: question about assigning null to a reference object
    ... String getAuthor() ... void setAuthor ... b.setTitle("Thinking in Java 4th Edition"); ...
    (comp.lang.java.help)
  • Re: Java questions: Urgent
    ... why I would expect almost any Java programmer to be able to answer ... Which is the main reason I "butted" in a bit.. ... on the characters in the String. ... > therefore naturally cover all the basics, or they have missed out badly ...
    (comp.lang.java.programmer)
  • Re: Using Cobol when writing CGIs for the OSU web server.
    ... string safe as well as make slow conversion (as bugs are found and ... The string type approach. ... Because no one has bothered to add it to the "offending" language. ... Java is certainly no replacement for C. ...
    (comp.os.vms)
  • Re: A C++ Whishlist
    ... with the C++ string classes as compared with the Java ones. ... You can keep you structs entirely ... The simple separation of interface and implementation that header files ...
    (comp.lang.cpp)