Groovy Cheat Sheet

println "Hello, World!"
// or
System.out.println("Hello, World!")

def x = 10
def y = 20
println x + y  // No semicolons needed

// Single line comment

/*
 * Multi-line
 * comment
 */

groovy script.groovy
groovy -e 'println "Hello"'  // One-liner

def name = "Groovy"  // Type inferred
def count = 42
def price = 19.99
def flag = true

String name = "Groovy"
int count = 42
double price = 19.99
boolean flag = true

def name = "World"
def msg = "Hello, $name!"  // Hello, World!
def calc = "2 + 2 = 4"  // 2 + 2 = 4

def multiline = """This is a
multi-line
string"""

println name.getClass()  // class java.lang.String
println count instanceof Integer  // true

def sum = a + b
def diff = a - b
def prod = a * b
def quot = a / b
def mod = a % b
def power = a ** b  // Exponentiation

a == b   // Equal
a != b   // Not equal
a > b
a < b
a >= b
a <= b
a <=> b  // Spaceship (compareTo)

a && b   // AND
a || b   // OR
!a       // NOT

def name = person?.name  // Null-safe access
def upper = str?.toUpperCase()

def name = inputName ?: "Default"
def value = nullableValue ?: 0

def list = [1, 2, 3]
def expanded = [0, *list, 4]  // [0, 1, 2, 3, 4]

if (age >= 18) {
    println "Adult"
} else {
    println "Minor"
}

if (str) { }        // Non-empty string is true
if (list) { }       // Non-empty collection is true
if (0) { }          // 0 is false!
if (null) { }       // null is false

def result = (age >= 18) ? "Adult" : "Minor"

switch (value) {
    case 1:
        println "One"
        break
    case 2..5:
        println "Between 2 and 5"
        break
    case [6, 7]:
        println "Six or Seven"
        break
    default:
        println "Other"
}

for (i in 1..10) {
    println i
}

def fruits = ["Apple", "Banana", "Orange"]
for (fruit in fruits) {
    println fruit
}

(1..10).each { i ->
    println i
}

def i = 0
while (i < 10) {
    println i
    i++
}

5.times {
    println "Hello"
}

5.times { i ->
    println "Iteration $i"
}

for (i in 1..100) {
    if (i == 50) break
    if (i % 2 == 0) continue
    println i
}

def greet = { name ->
    println "Hello, $name"
}
greet("Alice")

def square = { it * it }
println square(5)  // 25

def add = { a, b ->
    a + b
}
println add(5, 3)  // 8

def repeat(n, closure) {
    n.times { closure() }
}

repeat(3) {
    println "Hello"
}

def doubled = [1, 2, 3].collect { it * 2 }
println doubled  // [2, 4, 6]

def list = [1, 2, 3, 4, 5]
list << 6  // Append
list[0] = 10  // Update
println list.size()

list.each { println it }
def evens = list.findAll { it % 2 == 0 }
def doubled = list.collect { it * 2 }
def sum = list.sum()

def person = [name: "John", age: 30]
println person.name  // "John"
println person['age']  // 30
person.city = "NYC"  // Add new key

person.each { key, value ->
    println "$key: $value"
}

def range = 1..10  // Inclusive
def exclusive = 1..<10  // Exclusive
println 5 in range  // true

class Person {
    String name
    int age

    def greet() {
        println "Hello, I'm $name"
    }
}

def person = new Person(name: "John", age: 30)
person.greet()

class Person {
    String name
    int age

    Person(String name, int age) {
        this.name = name
        this.age = age
    }
}

trait Flyable {
    void fly() {
        println "Flying"
    }
}

class Bird implements Flyable {
    String name
}