Java Reference
In-Depth Information
This code compiles and runs without throwing an exception. However, the code contains a
defect that Challenge 18.5 brings out.
CHALLENGE 18.5
The following lines of code create a simulation object of a mixer in bay 1 and a copy
for bay 2:
package com.oozinoz.simulation;
import com.oozinoz.units.*;
public class ShowCloningProblem implements UnitConstants
{
public static void main(String[] args)
{
// Mixer 1 is in bay 1, at coordinate(15m, 25m)
Length x = (Length) METER.times(15);
Length y = (Length) METER.times(25);
Location loc = new Location(1, x, y);
// 10 hours mean-time-between-failure
MixerSimulator m1 =
new MixerSimulator(loc, (Time) HOUR.times(10));
MixerSimulator m2 = (MixerSimulator) m1.clone_1();
// Mixer 2 is in bay 2, at coordinate (20, 75)
m2.location.setBay(2);
m2.location.setCoordinates(
(Length) METER.times(20),
(Length) METER.times(75));
System.out.println(m1.location.bay);
}
}
Draw a diagram of the objects created by this code. Also, write down the results of
the
println()
statement.
You might want to make
Location
objects immutable, removing the class's
set
methods,
so that any number of clients could safely share a reference to the same location. At Oozinoz,
however, machine locations do occasionally change. Rather than making
Location
objects
immutable, you can fix the problem with
MachineSimulator.clone()
by making
Location
objects cloneable.
CHALLENGE 18.6
Suppose that you change the
Location
class to declare that it implements
Cloneable
and write a properly functioning
clone()
method for it. Now write
a revised version of the
clone()
method for the
MachineSimulator
class.
