data structures - Implementing my own tree Iterator in Java -

i trying implement iterator interface tree traversal. getting following error."incompatible types @ for(integer node : tr )" , "treeiterator.java uses unchecked or unsafe operations." unable fix error. can point out problem.

//class implement iterator interace. class inorderitr implements iterator {        public inorderitr(node root) {        st = new stack<node>();        this.root = root;     }      @override     public boolean hasnext() {         //has next     }      @override     public integer next(){           //next node     }      @override      public void remove(){         throw new java.lang.unsupportedoperationexception("remove not supported.");     } }  //this class makes sure use foreach loop. class inordertreeiterator implements iterable {      node root = null;      public inordertreeiterator(node root){         this.root = root;     }      @override     public iterator<integer> iterator(){         try{             return new inorderitr(this.root);         } catch(unsupportedoperationexception e){             system.out.println(e.getmessage());             return null;         }     } }   class treeiterator {      public static void main(string arg[]){         treeiterator obj = new treeiterator();         //create tree.         inordertreeiterator tr = new inordertreeiterator(obj.root);         for(integer node : tr ){             system.out.println(node);         }     } } 

ps: first try @ implementing iterator interface. if there standard practices not following please point out.

thank

iterable generic interface. means, unless give type parameter, raw type, , underlying data treated object.

change this:

class inorderitr implements iterator class inordertreeiterator implements iterable 

to following:

class inorderitr implements iterator<integer> class inordertreeiterator implements iterable<integer> 

this way, no longer raw type (and rids of warnings of unchecked , unsafe operations compiler gives currently), , tells compiler iterator have underlying data type integer (since type parameter in iterator interface underlying data type), type matches.