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javaexceptiontry-catchthrow

Java catching exceptions and subclases

Hello,

In Java if a method like BufferedReader.read() says it can throw an IOException and I try to catch a FileNotFoundException and an IOException in two catch blocks, what catch blocks will be entered if the file doesn't exist?

Does it enter only the most specific or both?

Solution

  • The first coded catch that matches the exception will be entered.
    Edited to incorporate comment from Azodius

    For example:

    try {
   bufferedReader.read();
} catch (FileNotFoundException e) {
   // FileNotFoundException handled here
} catch (IOException e) {
   // Other IOExceptions handled here
}

    This following code does not compile: 

    try {
   bufferedReader.read();
} catch (IOException e) {
   // All IOExceptions (and of course subclasses of IOException) handled here
} catch (FileNotFoundException e) {
   // Would never enter this block, because FileNotFoundException is a IOException
}

    Compiler message says:

    Unreachable catch block for FileNotFoundException. It is already handled by the catch block for IOException