Why do I get the Unhandled exception type IOException

Question

I have the following simple code   import java io    class IO       public static void main String   args               BufferedReader stdIn   new BufferedReader new InputStreamReader System in               String userInput             while   userInput   stdIn readLine       null              System out println userInput                      And I get the following error message   ---------- 1  ERROR in io java  at line 10      while   userInput   stdIn readLine       null                                             Unhandled exception type IOException ---------- 1 problem  1 error roman roman-laptop   work java  mcedit io java    Does anybody have any ideas why  I just tried to simplify the code given on the sum web site  here   Did I oversimplify

User · Answer

Java has a feature called  checked exceptions   That means that there are certain kinds of exceptions  namely those that subclass Exception but not RuntimeException  such that if a method may throw them  it must list them in its throws declaration  say  void readData   throws IOException  IOException is one of those   Thus  when you are calling a method that lists IOException in its throws declaration  you must either list it in your own throws declaration or catch it   The rationale for the presence of checked exceptions is that for some kinds of exceptions  you must not ignore the fact that they may happen  because their happening is quite a regular situation  not a program error  So  the compiler helps you not to forget about the possibility of such an exception being raised and requires you to handle it in some way   However  not all checked exception classes in Java standard library fit under this rationale  but that s a totally different topic

User · Answer

I got the Error even though i was catching the exception      try           bitmap   BitmapFactory decodeStream getAssets   open  quot kitten jpg quot           catch  IOException e            Log e  quot blabla quot    quot Error quot   e           finish           Issue was that the IOException wasn t imported import java io IOException

User · Answer

add  throws IOException  to your method like this   public static void main String args    throws  IOException           FileReader reader new FileReader  db properties             Properties p new Properties            p load reader

User · Answer

You should add  throws IOException  to your main method   public static void main String   args  throws IOException       You can read a bit more about checked exceptions  which are specific to Java  in JLS

User · Answer

Reading input from keyboard is analogous to downloading files from the internet  the java io system opens connections with the source of data to be read using InputStream or Reader  you have to handle a situation where the connection can break by using IOExceptions  If you want to know exactly what it means to work with InputStreams and BufferedReader this video shows it

User · Answer

Try again with this code snippet   import java io     class IO       public static void main String   args                try               BufferedReader stdIn   new BufferedReader new InputStreamReader System in                    String userInput                  while   userInput   stdIn readLine       null                    System out println userInput                           catch IOException ie                ie printStackTrace                           Using try-catch-finally is better than using throws  Finding errors and debugging are easier when you use try-catch-finally

[java] Why do I get the "Unhandled exception type IOException"?

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