Why do I get “Exception; must be caught or declared to be thrown” when I try to compile my Java code?

Question

Consider:

import java.awt.*;

import javax.swing.*;
import java.awt.event.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.*;
impor         


        

Answer 1

You'll need to decide how you'd like to handle exceptions thrown by the encrypt method.

Currently, encrypt is declared with throws Exception - however, in the body of the method, exceptions are caught in a try/catch block. I recommend you either:

• remove the throws Exception clause from encrypt and handle exceptions internally (consider writing a log message at the very least); or,
• remove the try/catch block from the body of encrypt, and surround the call to encrypt with a try/catch instead (i.e. in actionPerformed).

Regarding the compilation error you refer to: if an exception was thrown in the try block of encrypt, nothing gets returned after the catch block finishes. You could address this by initially declaring the return value as null:

public static byte[] encrypt(String toEncrypt) throws Exception{
  byte[] encrypted = null;
  try {
    // ...
    encrypted = ...
  }
  catch(Exception e){
    // ...
  }
  return encrypted;
}

However, if you can correct the bigger issue (the exception-handling strategy), this problem will take care of itself - particularly if you choose the second option I've suggested.