Java 天地·Core Java·Lecture Notes·Unitt4 - Control of execution

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Content Page # 4

Selection: IF匛LSE with compound statements

Just as the statement to execute for an if statement be a compound statement, so also can the statement following else be a compound statement. In fact, as a general rule in Java, wherever there is a single statement, braces can be inserted and a compound statement can be introduced.

For example, we might wish to perform more than one action if the temperature is too high, and more that one action otherwise:

if (temperature > 78)
{
soundAlarm();
displayFlashingLight( red );
triggerAlarmAtFireStation();

         }
          else
             displayFlashingLight( green );

Or perhaps, perform multiple actions in either case (so as well as the fire alarm device flashing a green light if the temperature is not too hot, it also sends a message to test the heating system in case the temperature is too cool):

if (temperature > 78)
{
soundAlarm();
displayFlashingLight( red );
triggerAlarmAtFireStation();
}

          else
          {
             displayFlashingLight( green );
             testHeatingSystem()
          }

Or perform a single action if the test is true, and multiple actions if the test is false:

if (temperature > 78)
soundAlarm();

          else
          {
            displayFlashingLight( green );
            testHeatingSystem()

}

Exercise 1 ?if' test

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