What's the IO Exception?

Question

Whenever I try to create a output file, it always
appear: IOException; must be caught or declared to be thrown.
What's the meaning?
Thanks in advance.

Answer 1

Exceptions are Java's and many other Object Orientated Language's means for error handling. When you try to open a file there may be many errors, like maybe the file dosent exist, right? To handle this in java you enclose the code that may throw exceptions, or erros, in a try/catch block, catching exceptions that may occur and doing whatever is necessary to inform the user or attempt something else...
example for you would be:
InputStreamReader in = null;
try {
in = new InputStreamReader(FileInputStream("test.txt"), "8859_1");
} catch (IOException e) {
System.out.println("Failed to open file: "+e.toString());