A set of sets

Question

I was trying to create a Set of sets of strings earlier today but getting an odd error from the compiler. My code looked something like this.
Set< Set<String> > finalSet = new LinkedHashSet< LinkedHashSet< String> >();and the compiler error was as follows
Controller.java:27: incompatible types
found   : java.util.LinkedHashSet<java.util.LinkedHashSet<java.lang.String>>
required: java.util.Set<java.util.Set<java.lang.String>>
                Set< Set<String> > finalSet = new LinkedHashSet< LinkedHashSet< String> >();Neither me nor anyone i know could see anything wrong with my code and i still havent figured out why it couldnt upcast the LinkedHashSet up to a set. When i changed my code to the following it worked fine though
LinkedHashSet< LinkedHashSet<String> > finalSet = new LinkedHashSet< LinkedHashSet< String> >();Also, when i changed my code to that I got another error in a later function which looks like this
finalSet.add((LinkedHashSet<String>)getResults.parse(regex, args[0]));getResults.parse() returns a set of strings but until i put the cast (LinkedHashSet<String>) on that result i was getting the following error
Controller.java:29: cannot find symbol
symbol  : method add(java.util.Set)
location: class java.util.LinkedHashSet<java.util.LinkedHashSet<java.lang.String>>
                finalSet.add(getResults.parse(regex, args[0]));which strikes me as a bit odd. Why couldnt it find the add method?
The entire thing confused me quite a bit so any help would be appreciated.
Thanks,
Sean

Answer 1

Or you could try this (untested) code:
Set< Set<String>> finalSet = new LinkedHashSet< Set<String>>();
String[] sa1 = {"a","b","c"};
String[] sa2 = {"d","e","f"};
Set<String> set1 = new LinkedHashSet<String>(Arrays.asList(sa1));
Set<String> set2 = new LinkedHashSet<String>(Arrays.asList(sa2));
finalSet.add(set1);
finalSet.add(set2);
System.out.println(finalSet);