I am supposed to Use Scanner to read int values from a file “input.txt”, Read until end of file is reached, Write all program output to a file “output.txt”, Write all exceptions to a file “error.txt”, and Output each number read.
I understand exceptions for the most part, but I do not understand how to write all exceptions to a text file in Java...
Like I wrote in my comment, write a try ... catch block where you write the exception to File error.txt using Printwriter.
For instance:
PrintWriter writer = new PrintWriter("error.txt");
try {
//Code to try goes here
} catch (Exception e) {
//You've got an exception. Now print it to error.txt
writer.write(e.toString());
}
You could test with something simple like:
PrintWriter writer = new PrintWriter("error.txt");
int[] i = new int[1];
try {
i[10] = 2;
} catch (Exception e) {
writer.write(e.toString());
}
This results in error.txt being populated with:
java.lang.ArrayIndexOutOfBoundsException: 10
You can print the entire Stack Trace by doing
e.printStackTrace(writer);
Very important that you don't forget to close the PrintWriter or your file won't get printed to. Once you are done writing to the file, close with:
writer.close();
use log4j for logging purpose,
Also , configure it at Error level for printing error into different file.
from your java code, write below line will print whole stack-track to the log file.
commons-logging, it's use likewise:
log.error("Message", exception);
All exceptions have a method: getMessage() that will return the exception as a string. In addition, toString(), which all Java classes should have, gives a little bit more information, since it also calls getMessage().
