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Java bird watcher
* Renames arrays to bird-count * Copies about files from arrays to for-loops and foreach-loops. * Renames arrays to bird-watcher. * Adds about files for for and foreach loops. * Fixed file names in config.json. * Update languages/concepts/foreach-loops/about.md Co-authored-by: Erik Schierboom <erik_schierboom@hotmail.com> * Update languages/concepts/for-loops/about.md Co-authored-by: Erik Schierboom <erik_schierboom@hotmail.com> * Improved texts for for and foreach loops. * Updated authors. Co-authored-by: Erik Schierboom <erik_schierboom@hotmail.com>
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‎concepts/for-loops/about.md‎

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The [for loop][for-loop] provides a mechanism to execute a group of statements repeatedly.
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The loop consists of four parts:
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````java
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for (initialization; test; update)
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{
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// body
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}
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````
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The initialization sets an initial state for the loop.
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Typically it declares and sets a variable used in the test expression and update statement.
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For example:
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````java
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int i=1
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````
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The test expression tests if the loop should execute the body
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and execute the update statement.
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If the test evaluates to true the body and the update expression will be executed.
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If the expression evaluates to false neither the body nor the update statement will be executed and execution continues after the loop.
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An example of a test can be:
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````java
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i <= 10
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````
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After executing the loop body, the update expression increments/decrements the loop variable by some value.
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Example:
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````java
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i++
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````
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A for loop executing over each element in an array can look like this:
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```java
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char[] vowels = {'a', 'e', 'i', 'o', 'u'};
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for (int i = 0; i<vowels.length; i++) {
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// Output the vowel
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System.out.print(vowels[i]);
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}
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// => aeiou
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```
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A `for` loop does have some advantages over a `foreach` loop:
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- You can start or stop at the index you want.
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- You can use any (boolean) termination condition you want.
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- You can skip elements by customizing the incrementing of the loop variable.
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- You can process collections from back to front by counting down.
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- You can use `for` loops in scenarios that don't involve collections.
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[for-loop]: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html

‎concepts/for-loops/links.json‎

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[
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{
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"link": "https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html",
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"description": "for-loop"
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}
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]

‎concepts/foreach-loops/about.md‎

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The [foreach loop][foreach-loop] provides a mechanism for executing a statement group for each element in a collection or array.
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Syntax:
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`````java
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for(declaration: collection) {
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// body
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}
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`````
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The declaration part declares the variable used to hold the values assigned from the collection:
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The collection is an array or a collection holding the values that will be assigned to the loop variable.
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The body contains the statements that will be executed once for each value in the collection.
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Example:
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```java
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char[] vowels = {'a', 'e', 'i', 'o', 'u'};
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for(char vowel:vowels) {
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// Output the vowel
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System.out.print(vowel);
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}
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// => aeiou
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```
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Generally a `foreach` loop is preferrable over a `for` loop for the following reasons:
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- A `foreach` loop is guaranteed to iterate over _all_ values. With a `for` loop, it is easy to miss elements, for example due to an off-by-one error.
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- A `foreach` loop is more _declarative_, your code is communicating _what_ you want it to do, instead of a `for` loop that communicates _how_ you want to do it.
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- A `foreach` loop is foolproof, whereas with `for` loops it is easy to have an off-by-one error.
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- A `foreach` loop works on all collection types, including those that don't support using an indexer to access elements.
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To guarantee that a `foreach` loop will iterate over _all_ values, the compiler will not allow updating of a collection within a `foreach` loop:
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```java
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char[] vowels = ['a', 'e', 'i', 'o', 'u'];
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for(char vowel:vowels) {
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vowels = ['Y']; // This would result in a compiler error
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}
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```
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[foreach-loop]: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html
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‎concepts/foreach-loops/links.json‎

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[
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{
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"link": "https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html",
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"description": "foreach-loop"
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}
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]

‎exercises/concept/arrays/.meta/config.json‎

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exercises/concept/arrays/.docs/hints.md renamed to exercises/concept/bird-watcher/.docs/hints.md

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exercises/concept/arrays/.docs/instructions.md renamed to exercises/concept/bird-watcher/.docs/instructions.md

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## 1. Check what the counts were last week
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For comparison purposes, you always keep a copy of last week's counts nearby, which were: 0, 2, 5, 3, 7, 8 and 4. Implement the `BirdCount.getLastWeek()` method that returns last week's counts:
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For comparison purposes, you always keep a copy of last week's counts nearby, which were: 0, 2, 5, 3, 7, 8 and 4. Implement the `BirdWatcher.getLastWeek()` method that returns last week's counts:
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```java
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BirdCount.getLastWeek();
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BirdWatcher.getLastWeek();
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// => [0, 2, 5, 3, 7, 8, 4]
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```
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## 2. Check how many birds visited today
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Implement the `BirdCount.getToday()` method to return how many birds visited your garden today. The bird counts are ordered by day, with the first element being the count of the oldest day, and the last element being today's count.
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Implement the `BirdWatcher.getToday()` method to return how many birds visited your garden today. The bird counts are ordered by day, with the first element being the count of the oldest day, and the last element being today's count.
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```java
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int[] birdsPerDay = { 2, 5, 0, 7, 4, 1 };
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BirdCount birdCount = new BirdCount(birdsPerDay);
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BirdWatcher birdCount = new BirdWatcher(birdsPerDay);
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birdCount.getToday();
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// => 1
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```
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## 3. Increment today's count
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Implement the `BirdCount.incrementDayCount()` method to increment today's count:
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Implement the `BirdWatcher.incrementDayCount()` method to increment today's count:
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```java
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int[] birdsPerDay = { 2, 5, 0, 7, 4, 1 };
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BirdCount birdCount = new BirdCount(birdsPerDay);
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BirdWatcher birdCount = new BirdWatcher(birdsPerDay);
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birdCount.incrementDayCount();
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birdCount.getToday();
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// => 2
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```
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## 4. Check if there was a day with no visiting birds
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Implement the `BirdCount.hasDayWithoutBirds()` method that returns `true` if there was a day at which zero birds visited the garden; otherwise, return `false`:
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Implement the `BirdWatcher.hasDayWithoutBirds()` method that returns `true` if there was a day at which zero birds visited the garden; otherwise, return `false`:
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```java
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int[] birdsPerDay = { 2, 5, 0, 7, 4, 1 };
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BirdCount birdCount = new BirdCount(birdsPerDay);
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BirdWatcher birdCount = new BirdWatcher(birdsPerDay);
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birdCount.hasDayWithoutBirds();
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// => true
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```
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## 5. Calculate the number of visiting birds for the first number of days
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Implement the `BirdCount.getCountForFirstDays()` method that returns the number of birds that have visited your garden from the start of the week, but limit the count to the specified number of days from the start of the week.
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Implement the `BirdWatcher.getCountForFirstDays()` method that returns the number of birds that have visited your garden from the start of the week, but limit the count to the specified number of days from the start of the week.
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```java
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int[] birdsPerDay = { 2, 5, 0, 7, 4, 1 };
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BirdCount birdCount = new BirdCount(birdsPerDay);
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BirdWatcher birdCount = new BirdWatcher(birdsPerDay);
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birdCount.getCountForFirstDays(4);
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// => 14
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```
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## 6. Calculate the number of busy days
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Some days are busier that others. A busy day is one where five or more birds have visited your garden.
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Implement the `BirdCount.getBusyDays()` method to return the number of busy days:
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Implement the `BirdWatcher.getBusyDays()` method to return the number of busy days:
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```java
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int[] birdsPerDay = { 2, 5, 0, 7, 4, 1 };
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BirdCount birdCount = new BirdCount(birdsPerDay);
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BirdWatcher birdCount = new BirdWatcher(birdsPerDay);
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birdCount.getBusyDays();
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// => 2
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```

exercises/concept/arrays/.docs/introduction.md renamed to exercises/concept/bird-watcher/.docs/introduction.md

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‎exercises/concept/bird-watcher/.meta/config.json‎

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{
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"authors": [
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{
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"github_username": "samuelteixeiras",
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"exercism_username": "samuelteixeiras"
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},
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{
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"github_username": "ystromm",
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"exercism_username": "ystromm"
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}
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],
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"editor": {
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"solution_files": ["src/main/java/BirdWatcher.java"],
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"test_files": ["src/test/java/BirdWatcherTest.java"]
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},
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"forked_from": ["csharp/arrays"]
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}

exercises/concept/arrays/.meta/design.md renamed to exercises/concept/bird-watcher/.meta/design.md

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