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Java Basics General beginning Java language questions that don't fit in one of the more specific forums. Please specify what version.
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Old March 9th, 2006, 05:09 AM
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Default Java IO error

I am a newie in java IO encountering an odd error, my platform is osx tiger, java 1.5.

and program fragment is:

import java.io.*;
public static void main(String[] args) {
   byte[] b = {50, 50, 51, 32};

When compile it, get "unreported exception javaio.IOException; must be caught or declared to be thrown
    System.out.write(b) "

If I catch the IOException and rewrite it as:

try {System.out.write(b)}
catch (IOException e) {System.err.println(e) }

The above error is fixed. But if I rewrite "System.out.write(b)" as
"System.out.write(b, 2, 1)" getting a compile-time error again:

"exception java.io.IOException is never thrown in body of corresponding try statement
   catch(IOException e) {System.err.println(e)} "

At this stage, when remove the catch statement, compile-time error is fixed again. Can anyone tell me why? thx.

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Old March 20th, 2007, 11:37 PM
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we can specify
public static void main(String[] args) throws IOException {
this can solve u r problem

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Old March 26th, 2007, 07:25 AM
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If you see the API documentation for the PrintStream class [System.out object is of PrintStream class], the write(bytes[]) method is taken from its parent class FilterOutputStream class and it throws IOException; thats why you've to catch it if you're calling it. And the other form of write() method write(bytes[], off, len) its overridden in PrintStream class and doesn't throw any Exception it handles them in its implementation thats why you get an exception if try to use try..catch around it saying "exception java.io.IOException is never thrown in body of corresponding try statement" as it doesn't throw any exception you need not use try..catch for it.

hope this is helpful.

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