🚀 go-pugleaf

hi,ladies and gentlemen,
1 i want to step into the method toArray(Object[]) of class
java.util.LinkedHashSet ,but when i clicked the button "Step into",it just
stepped over it,why? Moreover,when i put the class java.util.LinkedHashSet
into my project,it also can't step into? would you like to give me some
reasons?
2 My codes is as follows:
 ArrayList al=new ArrayList();
al.add("a");
al.add("b");
al.add("c");
LinkedHashSet lset=new LinkedHashSet(al);
String[] ss=new String[1];//array ss has a element
lset.toArray(ss);//please see the source of method toArray(Object[] a) in
the class java.util.LinkedHashSet
                 //it annouces that it can enlarge the  size of array a ,but
when the size of array of real                               //parameter  is
less than the size of set,it will throw an exception,why?
for(int i=0;i<ss.length();i++)
    System.out.print(ss[i]);   // there's an nullpointer exception