Java Reference
In-Depth Information
The definition of
getIndexOf
will be like the definition of
contains
, which we recall here:
public boolean
contains(T anEntry)
{
boolean
found =
false
;
for
(
int
index = 0; !found && (index < numberOfEntries); index++)
{
if
(anEntry.equals(bag[index]))
{
found =
true
;
}
// end if
}
// end for
return
found;
}
// end contains
The structure of the loop is suitable for the method
getIndexOf
, but we must save the value of
index
when the entry is found. The method will return this index instead of a boolean value.
2.28
The definition of
getIndexOf
.
To revise the loop in
contains
for use in
getIndexOf
, we define an
integer variable
where
to record the value of
index
when
anEntry
equals
bag[index]
. Thus, the
definition of
getIndexOf
looks like this:
// Locates a given entry within the array bag.
// Returns the index of the entry, if located, or -1 otherwise.
private int
getIndexOf(T anEntry)
{
int
where = -1;
boolean
found =
false
;
for
(
int
index = 0; !found && (index < numberOfEntries); index++)
{
if
(anEntry.equals(bag[index]))
{
found =
true
;
where = index;
}
// end if
}
// end for
// Assertion: If where > -1, anEntry is in the array bag, and it
// equals bag[where]; otherwise, anEntry is not in the array
return
where;
}
// end getIndexOf
The method
getIndexOf
returns the value of
where
. Notice that we initialize
where
to -1, which is
the value to return if
anEntry
is not found.
Question 16
What
assert
statement can you add to the definition of the method
getIndexOf
just before the
return
statement to indicate the possible values that the method can return?
Question 17
Revise the definition of the method
getIndexOf
so that it does not use a
boolean variable.
