Difference between revisions of "PowersOf2Iterable"
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interface [https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html Iterator<T>] | interface [https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html Iterator<T>] | ||
| − | <youtube>4ycpqdJ4yb4</youtube> | + | {{CollapsibleYouTube|Implementing Iterable and Iterator|<youtube>4ycpqdJ4yb4</youtube>}} |
=Mistakes To Avoid= | =Mistakes To Avoid= | ||
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{{warning | Do NOT confuse [https://docs.oracle.com/javase/8/docs/api/java/lang/Iterable.html Iterable<T>] from [https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html Iterator<T>]}} | {{warning | Do NOT confuse [https://docs.oracle.com/javase/8/docs/api/java/lang/Iterable.html Iterable<T>] from [https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html Iterator<T>]}} | ||
| − | = | + | =Client= |
| − | + | {{Client|PowersOfTwoLessThanClient|iteration.powersoftwo.client|main}} | |
| − | |||
| − | } | ||
| − | + | {{CollapsibleCode|PowersOfTwoLessThanClient| | |
| + | <syntaxhighlight lang="java"> | ||
| + | for (int powerOf2 : new PowersOfTwoLessThan(231)) { | ||
| + | System.out.println(powerOf2); | ||
| + | } | ||
| + | </syntaxhighlight>}} | ||
| − | + | {{CollapsibleConsole|PowersOfTwoLessThanClient Output|<pre style="border: 0px; background: #000; color:#fff;">1 | |
2 | 2 | ||
4 | 4 | ||
| Line 42: | Line 45: | ||
16 | 16 | ||
32 | 32 | ||
| − | 64</ | + | 64 |
| + | 128</pre>}} | ||
=Code to Implement= | =Code to Implement= | ||
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{{Sequential|public Iterator<Integer> iterator()}} | {{Sequential|public Iterator<Integer> iterator()}} | ||
| − | + | You can create an [https://docs.oracle.com/javase/tutorial/java/javaOO/anonymousclasses.html anonymous inner class] or a named class if you prefer. | |
| + | |||
| + | Note: if you type the following, and hover over the red line, IntelliJ will offer you to "Implement methods" necessary to create an anonymous inner class. You only need to override the '''hasNext()''' and '''next()''' methods. | ||
| + | |||
| + | <syntaxhighlight lang="java"> | ||
| + | return new Iterator<>() { | ||
| + | // Implement/Override necessary methods | ||
| + | }; | ||
| + | </syntaxhighlight> | ||
=Testing Your Solution= | =Testing Your Solution= | ||
Latest revision as of 03:17, 18 August 2023
Contents
Motivation
- Gain experience with implementing interfaces.
- Build a utility which will come in handy later in the semester (for example, the Scan exercise).
Investigate
interface Iterable<T>
interface Iterator<T>
| Video: Implementing Iterable and Iterator |
|---|
Mistakes To Avoid
 Warning: Do NOT Parallelize |
| Warning: Do NOT confuse Iterable<T> from Iterator<T> |
Client
| class: | PowersOfTwoLessThanClient.java | CLIENT |
| package: | iteration.powersoftwo.client | |
| source folder: | student/src/main/java |
| PowersOfTwoLessThanClient |
|---|
for (int powerOf2 : new PowersOfTwoLessThan(231)) {
System.out.println(powerOf2);
}
|
| PowersOfTwoLessThanClient Output |
|---|
1 2 4 8 16 32 64 128 |
Code to Implement
It is important to consider what state each class should encapsulate. The class PowersOfTwoLessThan, which is Iterable, should be have need to store little (if anything) beyond the maxExclusive passed in to its constructor. Further, PowersOfTwoLessThan should be immutable. There is no need to change any of the data during its lifetime.
The Iterator<Integer> instances created whenever one invokes the iterator() method? Now, the data for those instances are going to need to mutate.
One should NOT need to create a List to support this class. A single private final int instance variable is all you need for PowersOfTwoLessThan and a single (mutable) int instance variable is all you need for its Iterator.
| class: | PowersOfTwoLessThan.java |  |
| methods: | constructor iterator |
|
| package: | iteration.powersoftwo.exercise | |
| source folder: | student/src/main/java |
constructor
constructor: public PowersOfTwoLessThan(int maxExclusive)
iterator
method: public Iterator<Integer> iterator() 
(sequential implementation only)
You can create an anonymous inner class or a named class if you prefer.
Note: if you type the following, and hover over the red line, IntelliJ will offer you to "Implement methods" necessary to create an anonymous inner class. You only need to override the hasNext() and next() methods.
return new Iterator<>() {
// Implement/Override necessary methods
};
Testing Your Solution
Correctness
| class: | _PowersOfTwoTestSuite.java |  |
| package: | iteration.powersoftwo.exercise | |
| source folder: | testing/src/test/java |
Pledge, Acknowledgments, Citations
| file: | studio-powers-of-two-iterable-pledge-acknowledgments-citations.txt |
More info about the Honor Pledge
