Tried on Solaris-9 JDK 1.5.0-beta3-b58.

TestCase :
import java.util.regex.*;

public class Test1 {
   
   public void check(String str1, String str2) {
      try {
            Pattern p = Pattern.compile(str1);
            Matcher m = p.matcher(str2);
            while(m.find()) {
                System.out.println(m.group());
            }
      }catch(Exception e) {
         e.printStackTrace();
      }
   }
   
   public static void main(String args[]) {
             
       Test1 ref = new Test1();
       ref.check(args[0], args[1]);
   }

}

Execute :

java Test1 "\P{javaUpperCase}" "J@v" Will work fine and gives the output as
@
v

But when we execute with the following

java Test1 "\p{javaUpperCase}\P{javaUpperCase}+" "J@v" will throw the following exception..
java.lang.StringIndexOutOfBoundsException: String index out of range: 3
at java.lang.String.charAt(String.java:558)
at java.util.regex.Pattern.countChars(Pattern.java:2791)
at java.util.regex.Pattern.access$000(Pattern.java:595)
at java.util.regex.Pattern$Not.match(Pattern.java:3764)
at java.util.regex.Pattern$Curly.match0(Pattern.java:4222)
at java.util.regex.Pattern$Curly.match(Pattern.java:4196)
at java.util.regex.Pattern$JavaTypeClass.match(Pattern.java:3595)
at java.util.regex.Pattern$Start.match(Pattern.java:3019)
at java.util.regex.Matcher.search(Matcher.java:1092)
at java.util.regex.Matcher.find(Matcher.java:528)
at Test1.check(Test1.java:9)
at Test1.main(Test1.java:20)
 
The doc does not mention the behaviour when using P with java.lang.Character classes in regex.
Is the behaviour same as mentioned under Unicode.