public class TreeTest {
    public static void main(String[] args) {
        Set<TreeVo>  tree = new TreeSet<TreeVo>();
        TreeVo vo1 = new TreeVo(1,2);
        TreeVo vo2 = new TreeVo(2,3);
        TreeVo vo3 = new TreeVo(3,1);
        if(addTree(tree, vo1)){
            tree.add(vo1);
        }
        if(addTree(tree, vo2)){
            tree.add(vo2);
        }
        if(addTree(tree, vo3)){
            tree.add(vo3);
        }
        
    }
    
    public static boolean addTree(Set tree,TreeVo  vo){
        if(tree.contains(vo)){
            System.out.println("its fail because exit:"+ vo.getNext()); 
            return false;
        }else{
            System.out.println("its ok:" + vo.getNext());
            return true;
        }
    }

}