Assume that the classes listed in the Java Quick Reference have been imported where appropriate. Unless otherwise noted in the question, assume that parameters in method calls are not null and that methods are called only when their preconditions are satisfied.
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This question involves the implementation of the AddtionPattern class, which generates a number pattern. The AdditionPattern object is constructed with two positive integer parameters, as described below.
The first positive integer parameter indicates the starting number in the pattern.
The second positive integer parameter indicates the value that is to be added to obtain each subsequent number in the pattern.
The AdditionPattern class also supports the following methods.
currentNumber, which returns the current number in the pattern
next, which moves to the next number in the pattern
prev, which moves to the previous number in the pattern or takes no action if there is no previous number
The following table illustrates the behavior of an AdditionPattern object that is instantiated by the following statement.
AdditionPattern plus3 = new AdditionPattern(2, 3);
Method Call Value Returned Explanation
(blank if no value)
plus3.currentNumber(); 2 The current number is initially the
starting number in the pattern.
plus3.next(); The pattern adds 3 each time, so
move to the next number in the
pattern (5).
plus3.currentNumber(); 5 The current number is 5.
plus3.next(); The pattern adds 3 each time, so
move to the next number in the
pattern (8).
plus3.next(); The pattern adds 3 each time, so
move to the next number in the
pattern (11)
plus3.currentNumber(); 11 The current number is 11.
plus3.prev(); Move to the previous number in
the pattern (8).
plus3.prev(); Move to the previous number in
the pattern (5).
plus3.prev(); Move to the previous number in the
pattern (2).
plus3.currentNumber(); 2 The current number is 2.
plus3.prev(); There is no previous number in the
pattern prior to 2, so no action is
taken.
plus3.currentNumber(); 2 The current number is 2.