Comment 1 Olivier Thomann 2006-07-12 07:00:34 EDT

It compiles with javac 1.5.0_07, but not with javac 1.5.0_08.
X.java:8: inconvertible types
found   : java.util.Properties
required: java.util.Map<java.lang.String,?>
                for (Map.Entry<String, ?> entry : ((Map<String, ?>) props).entrySet()) {
                                                                    ^
1 error

import java.util.Map;
import java.util.Properties;

public class X {

	public static void main(String[] args) {
		Properties props = new Properties();
		for (Map.Entry<String, ?> entry : ((Map<String, ?>) props).entrySet()) {
			System.out.println(entry);
		}
	}
}
Also fail with javac 6.0b88. This looks like a fixed bug.

Comment 2 Max Rydahl Andersen 2006-07-12 07:05:41 EDT

ah, those pesky nano updates. sorry for bothering you ;)

Comment 3 Max Rydahl Andersen 2006-07-12 07:07:22 EDT

...just as sidenote: What rule is broken here ? (if you know)

Comment 4 Philipe Mulet 2006-07-12 10:58:25 EDT

Properties is not a subtype of Map<String,?>.
It inherits from Map<Object,Object>, which is provably distinct from Map<String,?>.

The following would work:
import java.util.Map;
import java.util.Properties;

public class X {

	public static void main(String[] args) {
		Properties props = new Properties();
		for (Map.Entry<Object, ?> entry : ((Map<Object, ?>) props).entrySet()) {
			System.out.println(entry);
		}
	}
}

or you could even use: Map.Entry<?, ?> entry : ((Map<?, ?>).
BTW, I don't get what the cast buys you here.

Comment 5 Philipe Mulet 2006-07-12 11:01:20 EDT

It works as per design.
Added GenericTypeTest#test1023

Comment 6 Max Rydahl Andersen 2006-07-12 13:03:24 EDT

i understand. the only thing it bought were no need to cast the key to a string.