Handling Exceptions and Debugging - Beginning Java Programming: The Object-Oriented Approach - page 206

}
public static void recalculate(double fundAmount, double rate) {
fundAmount = fundAmount * (1 + rate);
}
6. Now, replace the System.out.println() statement with a log message: logger.
fatal("monthlyPension is too low.");
7. Next, add some messages to test the different levels of the logger at the end of the main
method.
log.trace("finely detailed TRACE message");
log.debug("detailed DEBUG message");
log.info("informational message");
log.warn("warning message");
log.error("error message");
log.fatal("fatal message");
8. Finally, add log messages to the recalculate() method.
log.entry();
fundAmount = fundAmount * (1 + rate);
log.info("fundAmount = " + fundAmount);
log.exit();
9. Your class should now look like this:
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;
public class ApacheLogging {
static final Logger log = LogManager.getLogger(ApacheLogging.class.getName());
public static void main(String[] args) {
int age = 60;
double retirementFund = 10000;
int yearsInRetirement = 20;
String name = "David Johnson";
for (int i = age; i <= 65; i++) {
recalculate(retirementFund, 0.1);
}
double monthlyPension = retirementFund / yearsInRetirement / 12;
System.out.println(name + " will have $" + monthlyPension
+ " per month for retirement.");
if (monthlyPension < 100) {
log.fatal("monthlyPension is too low");
}
// create a series of log entries to show which
// levels are printed to which handler's log
log.trace("finely detailed TRACE message");
log.debug("detailed DEBUG message");
log.info("informational message");