Sets don't deserialise to something that equals the original

[IanRogers]

The following junit test fails at the last assert with the error:

java.lang.AssertionError: expected: java.util.HashSet<[1]> but was: java.util.HashSet<[1]>

@Test
public void test_Set() throws YamlException {
    Set<Integer> set1 = new HashSet<Integer>(); 
    set1.add(1);
    Set<Integer> set2 = new HashSet<Integer>();
    set2.add(1);
    assertEquals(set1, set2);

    // serialise
    Writer sb = new StringWriter();
    YamlWriter writer = new YamlWriter(sb);        
    writer.write(set1);
    writer.close();
    String yaml = sb.toString();

    // deserialise
    YamlReader reader = new YamlReader(new StringReader(yaml));
    Set<Integer> set3 = (Set<Integer>) reader.read();
    assertEquals(set1, set3);
}

The yaml is:

!java.util.HashSet
- 1

[NathanSweet]

Java uses erasure for generics. There is no way to know what the generic type of the local variable set is, so you get a string "1" and not an Integer 1. If you want that to work, you could use a class with a field of type Set<Integer>, since the generic type on the field is not erased.

    static public class Meow {
        public Set<Integer> set = new HashSet();
    }

    public void test_Set () throws YamlException {
        Meow meow1 = new Meow();
        meow1.set.add(1);
        Meow meow2 = new Meow();
        meow2.set.add(1);
        assertEquals(meow1.set, meow2.set);

        // serialise
        Writer sb = new StringWriter();
        YamlWriter writer = new YamlWriter(sb);
        writer.write(meow1);
        writer.close();
        String yaml = sb.toString();
        System.out.println(yaml);

        // deserialise
        YamlReader reader = new YamlReader(new StringReader(yaml));
        Meow meow3 = (Meow)reader.read();
        assertEquals(meow1.set, meow3.set);
    }

However, this has not been implemented for YamlBeans. I don't have time at the moment, but you could look at JsonBeans to see how it could be done:
https://github.com/EsotericSoftware/jsonbeans/blob/master/src/com/esotericsoftware/jsonbeans/Json.java#L980

Contributions are welcome!