Groovy: added installation, colletions, maps, beans, logical branching and loops

groovy.html.markdown

@@ -10,6 +10,177 @@ Groovy - A dynamic language for the Java platform [Read more here.](http://groov
 
 ```cpp
 
+/*
+  Set yourself up:
+
+  1) Install GVM - http://gvmtool.net/
+  2) Install Groovy: gvm install groovy
+  3) Start the groovy console by typing: groovyConsole
+
+*/
+
+//  Single line comments start with two forward slashes
+/*
+Multi line comments look like this.
+*/
+
+// Hello World
+println "Hello world!"
+
+/*
+  Variables:
+
+  You can assign values to variables for later use
+*/
+
+def x = 1
+println x
+
+x = new java.util.Date()
+println x
+
+x = -3.1499392
+println x
+
+x = false
+println x
+
+x = "Groovy!"
+println x
+
+/*
+  Collections and maps
+*/
+//Creating an empty list
+def technologies = []
+
+//Add an element to the list
+technologies << "Groovy"
+technologies.add("Grails")
+technologies.addAll(["Gradle","Griffon"])
+
+//Remove an element from the list
+technologies.remove("Griffon")
+
+//Iterate over elements of a list
+technologies.each { println "Technology: $it"}
+technologies.eachWithIndex { it, i -> println "$i: $it"}
+
+//Evaluate if a list contains element(s) (boolean)
+technologies.contains('Groovy')
+technologies.containsAll(['Groovy','Grails'])
+
+//Sort a list
+technologies.sort()
+
+//Replace all elements in the list
+Collections.replaceAll(technologies, 'Gradle', 'gradle')
+
+//Shuffle a list
+Collections.shuffle(technologies, new Random())
+
+//Clear a list
+technologies.clear()
+
+//Creating an empty map
+def devMap = [:]
+
+//Add values
+devMap = ['name':'Roberto', 'framework':'Grails', 'language':'Groovy']
+devMap.put('lastName','Perez')
+
+//Iterate over elements of a map
+devMap.each { println "$it.key: $it.value" }
+devMap.eachWithIndex { it, i -> println "$i: $it"}
+
+//Evaluate if a map contains a key
+assert devMap.containsKey('name')
+
+//Evaluate if a map contains a value
+assert devMap.containsValue('Roberto')
+
+//Get the keys of a map
+println devMap.keySet()
+
+//Get the values of a map
+println devMap.values()
+
+/*
+  Groovy Beans
+
+  GroovyBeans are JavaBeans but using a much simpler syntax
+
+  When Groovy is compiled to bytecode, the following rules are used.
+
+    * If the name is declared with an access modifier (public, private or protected) then a field is generated.
+    * A name declared with no access modifier generates a private field with public getter and setter (i.e. a property).
+    * If a property is declared final the private field is created final and no setter is generated.
+    * You can declare a property and also declare your own getter or setter.
+    * You can declare a property and a field of the same name, the property will use that field then.
+    * If you want a private or protected property you have to provide your own getter and setter which must be declared private or protected.
+    * If you access a property from within the class the property is defined in at compile time with implicit or explicit this (for example this.foo, or simply foo), Groovy will access the field directly instead of going though the getter and setter.
+    * If you access a property that does not exist using the explicit or implicit foo, then Groovy will access the property through the meta class, which may fail at runtime.
+
+*/
+
+class Foo {
+    // read only property
+    final String name = "Roberto"
+
+    // read only property with public getter and protected setter
+    String language
+    protected void setLanguage(String language) { this.language = language }
+
+    // dynamically typed property
+    def lastName
+}
+
+/*
+  Logical Branching and Looping
+*/
+
+//Groovy supports the usual if - else syntax
+def x = 3
+
+if(x==1) {
+    println "One"
+} else if(x==2) {
+    println "Two"
+} else {
+    println "X greater than Two"
+}
+
+//Groovy also supports the ternary operator:
+def y = 10
+def x = (y > 1) ? "worked" : "failed"
+assert x == "worked"
+
+//For loop
+//Iterate over a range
+def x = 0
+for (i in 0 .. 30) {
+    x += i
+}
+
+//Iterate over a list
+x = 0
+for( i in [5,3,2,1] ) {
+    x += i
+}
+
+//Iterate over an array
+array = (0..20).toArray()
+x = 0
+for (i in array) {
+    x += i
+}
+
+//Iterate over a map
+def map = ['name':'Roberto', 'framework':'Grails', 'language':'Groovy']
+x = 0
+for ( e in map ) {
+    x += e.value
+}
 
 ```