Designing Classes - Java Concepts - page 497

However, you should be aware of one common use of the this reference. When
implementing constructors, many programmers find it tiresome to come up with
different names for instance fields and parameters. Using the this reference
solves that problem. Here is a typical example.

public Coin(double value, String name)
{
this. value = value;
this.name = name;
}

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The expression this.value refers to the instance field, but value is the
parameter. Of course, you can always rename the construction parameters to
aValue and aName , as we have done in this topic.

S ELF C HECK

16. Consider the deposit method of the BankAccount class. What is
the scope of the variables amount and newBalance ?

17. What is the scope of the balance field of the BankAccount class?

C OMMON E RROR 8.2: Shadowing

Accidentally using the same name for a local variable and an instance field is a
surprisingly common error. As you saw in the preceding section, the local
variable then shadows the instance field. Even though you may have meant to
access the instance field, the local variable is quietly accessed. For some reason,
this problem is most common in constructors. Look at this example of an
incorrect constructor:

public class Coin
{
public Coin(double aValue, String aName)
{
value = aValue;
String name = aName; // Oops. . .
}
. . .
private double value;