groovy: Init helloworld example for groovy (#231)

topics/groovy/README.md

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+# Install groovy
+- See https://groovy-lang.org/install.html (I prefer using SDK man)
+- Facing missing java issue while installing: Visit: [groovy-with-sdk-missing-java.md](.././../troubleshooting/installation/groovy-with-sdk-missing-java.md)
+
+# Basic groovy scripting
+- See [helloworld](./helloworld/)

topics/groovy/helloworld/basic-concept.groovy

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+// Greetings!
+println "Welcome to groovy!"
+
+// Working with variables
+myName = "Tung"
+myAge = 28
+println "${myName} is ${myAge} years old!"
+
+// Working with if else
+def number = 10
+
+if (number > 5) {
+    println("The number is greater than 5.")
+} else {
+    println("The number is not greater than 5.")
+}
+
+// Working with switch case
+def myFruit = "Banana"
+
+switch (myFruit) {
+    case "Apple":
+        println("It's an apple.")
+        break
+    case "Banana":
+        println("It's a banana.")
+        break
+    case "Cherry":
+        println("It's a cherry.")
+        break
+    default:
+        println("It's something else.")
+}
+
+// Working with for loop
+def fruits = ["Apple", "Banana", "Cherry", "Watermelon", "Elderberry"]
+
+for (fruit in fruits) {
+    println("I like $fruit")
+}
+
+// Working with function
+def factorial(n) {
+    if (n == 0) {
+        return 1
+    } else {
+        return n * factorial(n - 1)
+    }
+}
+//-- Call the function and store the result in a variable
+def result = factorial(5)
+//-- Print the result
+println("Factorial of 5 is: $result")
+
+// Working with Map in groovy
+// Create a map with key-value pairs
+def person = [
+    "firstName": "John",
+    "lastName": "Doe",
+    "age": 30,
+    "city": "New York"
+]
+// Access values in the map
+def firstName = person["firstName"]
+def age = person["age"]
+// Modify values in the map
+person["city"] = "Los Angeles"
+// Add a new key-value pair to the map
+person["email"] = "john.doe@example.com"
+// Iterate over the map
+person.each { key, value ->
+    println("$key: $value")
+}
+
+// Working with try catch
+def divideNumbers(int dividend, int divisor) {
+    try {
+        def result = dividend / divisor
+        return result
+    } catch (ArithmeticException e) {
+        println("An arithmetic exception occurred: ${e.message}")
+    } finally {
+        println("Finally block executed.")
+    }
+}
+
+// Example usage:
+try {
+    def devideResult = divideNumbers(10, 2)
+    println("Result: $devideResult")
+} catch (Exception e) {
+    println("An exception occurred: ${e.message}")
+}

troubleshooting/installation/groovy-with-sdk-missing-java.md

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+# Groovy
+- Error `groovy: JAVA_HOME not set and cannot find javac to deduce location, please set JAVA_HOME.`:
+```
+➜  ~ curl -s "https://get.sdkman.io" | bash
+➜  ~ source "$HOME/.sdkman/bin/sdkman-init.sh"
+➜  ~ source "$HOME/.sdkman/bin/sdkman-init.sh"
+➜  ~ sdk install groovy
+
+Downloading: groovy 4.0.14
+
+In progress...
+
+##################################################################################################################################################################################### 100.0%
+
+Installing: groovy 4.0.14
+Done installing!
+
+
+Setting groovy 4.0.14 as default.
+➜  ~ groovy
+groovy: JAVA_HOME not set and cannot find javac to deduce location, please set JAVA_HOME.
+➜  ~ groovy --version
+groovy: JAVA_HOME not set and cannot find javac to deduce location, please set JAVA_HOME.
+➜  ~ sdk install java
+
+Downloading: java 17.0.8.1-tem
+
+In progress...
+
+##################################################################################################################################################################################### 100.0%
+
+Repackaging Java 17.0.8.1-tem...
+
+Done repackaging...
+
+Installing: java 17.0.8.1-tem
+Done installing!
+
+
+Setting java 17.0.8.1-tem as default.
+➜  ~ groovy --version
+Groovy Version: 4.0.14 JVM: 17.0.8.1 Vendor: Eclipse Adoptium OS: Linux
+➜  ~
+```