java - How to correctly throw an exception -


i'm new java , i'm trying account possible errors might come in program. i'm creating calculator , converting inputs infix postfix calculate result. want try accounting mismatched parenthesis in input, i'm having trouble. example, when converting infix postfix, when ) reached, pop numbers stack , put them onto new postfix list. in 1 case there may not matching left parenthesis present (the while loop reaches end of stack without coming across (, should throw exception. i've implemented following code, doesn't seem working:

    else if(tok.equals(")")){       while(stack.peek().equals("(") == false){         try{           operator o = stack.pop();           nlist.add(o);                         } catch(emptystackexception e){           system.out.println(e.getmessage());         }         stack.pop();       }

then in other file constructs gui , processes inputs, entered:

try{   java.util.list<token> postfix = expressionmanager.infixtopostfix(infix);   // build expression   expression exp = expressionmanager.buildexpression(postfix);   // display results }catch(arithmeticexception e){      entryfield.settext(e.getmessage()) }

any suggestions?

stack.peek() throws emptystackexception before enter inside try-catch block (i assume expect pop throw exception).

second block doesn't show how arithmeticexception thrown, so, not sure expecting here.


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