References

The file Person.java defines a simple class that represents a person (a person has a name and an age). The file References1.java contains a program that instantiates three Person objects and then makes some modifications to the objects and their references.

• Carefully hand-trace the References1.java program. Draw a diagram to illustrate the three objects and the references to them and how these change as the program executes. Your trace should also show what the program prints.
• Now compile and run the program. Compare the results to your trace. If there are any differences, re-trace the program to understand what it is doing.
• Suppose the programmer meant to do a circular shift in reassigning the three people -- that is he/she wanted to have the original person2 object become person1, the original person3 become person2 and the original person1 become person3. Revise the code to make this happen.

The file References2.java contains another program involving Person objects. This one illustrates the difference between assignments involving objects and assignments involving primitive values.

• Hand trace References2.java.
• Run the program to check your trace. If your trace was incorrect, study the program more carefully to understand what it is doing.
• Why do the three objects stay the same for all the different assignments but the three integers do not?