Question: For the following String creation within a trigger, I'm checking to see if the field is blank. If not, then it should use that field's value as the correct string, else, it should remain blank.

```
String sitenprodcomb = (String.isNotBlank(line.Site__c) ? line.Site__c : '') + String.valueof(line.ProductId__c);

```

However, I'm getting the String exception described in the title when I try to adjust the status of an object using this trigger, I get the error described in the title. 

[![enter image description here](https://i.stack.imgur.com/QQZsY.png)](https://i.stack.imgur.com/QQZsY.png)

Line 272 simply invokes the function that houses this string. The data is being moved into this function correctly. What alternatives do you suggest for setting this String to the correct value?

Answer: 
As mention you cannot hide the field but you can change the label like you asked.

Setup->Customize->Tab Names and Labels-> Rename Tabs and Labels

Click [Edit] next to opportunities then click [Next], you can rename the standard fields on the following screen.

Keep in mind that Close Date drives a lot of functionality in Salesforce and I would highly suggest you use the field for meaningful data even if you rename it.
I have a solution for this for now, I have created VF page where I am not showing close date then with the extension I am populating this fields and on save I am displaying the close date.