Using Command to Supply a Service
Suppose that you want to let developers time how long a method takes to execute. Figure 24.1 shows a Command interface and a time() utility that times the execution of a command.
Figure 24.1. The time() method returns the number of milliseconds that a command takes to execute.
The code for time() captures the system time before and after executing the command and returns the difference:
public static long time(Command c) { long t1 = System.currentTimeMillis(); c.execute(); long t2 = System.currentTimeMillis(); return t2 - t1; }
Suppose that you decide to test the time() method with an automated testing tool. ...
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