ArrayList is not initializing properly in java -

i using arraylist in application.
declared list<product> productlist = new arraylist<product>(); globally products not adding list because productlist showing null instead of empty array list.

below code:

map<string, list<product>> productlistmap = productsuggestbox.getvaluemap();  list<product> queriedproductlist = productlistmap.get("productlist");  long productid = long.valueof(productsuggestboxvalue);  (product product : queriedproductlist) {     if (product.getid() == productid) {         productlist.add(product);         break;     } } 

here attempt piece structure of code fragments provided:

public class salesinvoicewidget extends composite {      list<product> productlist = new arraylist<product>();      // ...      private void somemethod() {         map<string, list<product>> productlistmap =                  productsuggestbox.getvaluemap();          list<product> queriedproductlist = productlistmap.get("productlist");          long productid = long.valueof(productsuggestboxvalue);          (product product : queriedproductlist) {             if (product.getid() == productid) {                 productlist.add(product);                 break;             }         } 

assuming reconstruction above correct, way productlist can null somewhere in code (not shown above!), assigning null productlist.

another possible explanation different declaration of productlist in scope @ point seeing null; e.g. may local variable or method parameter named productlist shadowing "global" declaration.

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note variable in java cannot magically become null if non-null. either assigned it, or different variable. there no other plausible explanations ... assuming using pure java.