Update vector using threads

Question

I've got some threads in my program which will add elements to a static vector.
If two threads want to add the same data to the vector, there will be two exactly the same elements in the vector. How can I make sure there is no two elements containing the same data?
I've tried this, but there are still 2 same elements in the vector at the end.
     if (v.bufferedVector.contains(data)){
          System.out.println("I've got it");
          else{
          v.addElement(data);     
}

Answer 1

sorry, i didn't mean Comparable. i just meant put an equals in there. and put a hashCode() in there too...
class MyDataType implements java.lang.Comparable {
       int ID;
       String localVar;
       String destVar;
       int se;
       String[] data;
       public boolean equals(Object o) {
          MyDataType mdt = (MyDataType)o;
          //somehow determine how "this" equals mdt.
          //you might check all the internals of mdt
          //to "this"