Cannot use "class" as an attribute alias

Why can't I use "class" as an attribute name? Whenever I tried, an exception is thrown. Is this a bug or am I doing something wrong here? Please see the code below.

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.converters.SingleValueConverter;

public class Software {
private static class AttributeConverter implements SingleValueConverter {
@SuppressWarnings("unchecked")
@Override
public boolean canConvert(Class type)

{ return type.equals(Attribute.class); }

@Override
public String toString(Object obj)

{ return obj == null ? null : ((Attribute) obj).value; }

@Override
public Object fromString(String name)

{ return new Attribute(name); }

}

private static class Attribute {
public String value;

public Attribute(String value)

{ this.value = value; }

}

public Attribute clazz;

public static void main(String[] args)

{ String xml = "<software id=\"test\"/>"; // Using "id" as an attribute is fine, // String xml = "<software class=\"test\"/>"; // but using "class" won't work!! XStream xstream = new XStream(); xstream.alias("software", Software.class); xstream.aliasAttribute("id", "clazz"); // Using "id" as an alias is fine, //xstream.aliasAttribute("class", "clazz"); // but using "class" won't work!! xstream.useAttributeFor("clazz", Attribute.class); xstream.registerConverter(new AttributeConverter()); Software sw = (Software) xstream.fromXML(xml); System.out.println(xstream.toXML(sw)); }

}