Merge pull request #20 from brunobaiano/tip-17

tip-17

_posts/2023-11-15-daily-tip-17.md

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+---
+title: "Daily tip #17"
+date: 2023-11-15
+---
+
+## Tip of the day #17
+
+Stop imposing and start to declare your code. Declarative expressions are key to parallelism, 
+so you need to learn this path. 
+
+“This is the way”
+
+### Declarative vs Imperative Programming
+
+Imperative Programming is HOW the program does, step by step, sequence of commands. 
+
+Look at this piece of code (thanks to Russel Winder) :
+
+
+```java
+List<Integer> squareImperative(final List<Integer> datum) {
+    var result = new ArrayList<Integer>();
+    for (var i = 0; i < datum.size(); i++) {
+        result.add(i, datum.get(i) * datum.get(i));
+    }
+    return result;
+}
+```
+
+Declarative Programming is WHAT the program does, the expression, 
+without explicitly specifying its control flow.
+
+The same result before, but using parallelStream:
+
+
+```java
+List<Integer> squareDeclarative(final List<Integer> datum) {
+    return datum.parallelStream()
+        .map(i -> i * i)
+        .collect(Collectors.toList());
+}
+```
+
+Venkat Subramaniam has a book called “Functional Programming in Java”
+ where he mentions the benefits of declarative programming:
+
+* Nicely composed, not cluttered
+* Free of low-level operations
+* Easier to enhance or change the logic
+* Iteration controlled by a library of methods
+* Efficient; lazy evaluation of loops
+* Easier to parallelize where desired
+
+Cool right?  =D
+
+
+### How to use it
+
+This video is the best source to start it
+
+Refactoring from Imperative to Functional Style with Venkat Subramaniam
+https://www.youtube.com/watch?v=TG67kq7WUEo