code: public float l2Norm2() {
  		TIntFloatIterator it = data.iterator();
  		float norm = 0f;
  		while(it.hasNext()){
  			it.advance();
  			norm += it.value()*it.value();
  		}
  		return norm;
  	}
docs: /* (non-Javadoc)
  @see org.fnlp.ml.types.sv.ISparseVector#l2Norm2()