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Can explain logging

Logging is the deliberate recording of certain information during a program execution for future reference. Logs are typically written to a log file but it is also possible to log information in other ways e.g. into a database or a remote server.

Logging can be useful for troubleshooting problems. A good logging system records some system information regularly. When bad things happen to a system e.g. an unanticipated failure, their associated log files may provide indications of what went wrong and actions can then be taken to prevent it from happening again.

A log file is like the of an airplane; they don't prevent problems but they can be helpful in understanding what went wrong after the fact.



Can use logging

Most programming environments come with logging systems that allow sophisticated forms of logging. They have features such as the ability to enable and disable logging easily or to change the logging .

This sample Java code uses Java’s default logging mechanism.

First, import the relevant Java package:

import java.util.logging.*;

Next, create a Logger:

private static Logger logger = Logger.getLogger("Foo");

Now, you can use the Logger object to log information. Note the use of a for each message. When running the code, the logging level can be set to WARNING so that log messages specified as having INFO level (which is a lower level than WARNING) will not be written to the log file at all.

// log a message at INFO level
logger.log(Level.INFO, "going to start processing");
// ...
if (error) {
    // log a message at WARNING level
    logger.log(Level.WARNING, "processing error", ex);
// ...
logger.log(Level.INFO, "end of processing");



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