Arithmetic formulas in Java execution strings

When implementing an arithmetic formula in a string, the following code is used:

 Public Static string Stringfinalresult (string original) {              try  {                    = (string) jse.eval ( original);                   return temp;               Catch (Exception t) {                    returnnull;              }  }  

The console output is null after the function is called

The code should be modified to resemble the following:

 Public Static string Stringfinalresult (string original) {              try  {                    = jse.eval (original);                  =temp.tostring ();                   return result;               Catch (Exception t) {                    returnnull;              }  }  

The reason for the error is that Jse.eval () cannot force the type to be converted to string format, so the program executes a catch statement.

I found it by modifying the return value in the Catch statement.

Arithmetic formulas in the Java execution string