[Groovy] 기본 문법

println

println "Hello World"
println 'Hello World'
println("Hello World")

Variable

def name = "john"
String name = "john"
name = "john"

def (a, b, c) = [30, 40, 50]

println "${a} ${b} ${c}"  // 30, 40, 50
println "${a.getClass()} ${b.getClass()} ${c.getClass()}"  // class java.lang.Integer class java.lang.Integer class java.lang.Integer

def (String a, int b, Double c) = [30, 40, 50]

println "${a} ${b} ${c}"  // 30 40 50.0
println "${a.getClass()} ${b.getClass()} ${c.getClass()}"  // class java.lang.String class java.lang.Integer class java.lang.Double

Operator

println 2 ** 3  // 8
println 9.intdiv(5)  // 1
println 9 / 5  // 1.8

println Integer.toBinaryString(20)  // 10100
println Integer.parseInt("20") // 20

println !"foo"  // false
println !""  // true

def output = (1 > 0) ? "1 is greeter" : "1 is not greeter"

println output  // 1 is greeter

Conditional Statements

def x = 0.0

switch (x) {
    case 0:
        println "x is zero"
        break
    case { x > 0 }:
        println "x is +ve"
        break
    case {x < 0}:
        println "x is -ve"
        break
    default:
        println "Invalid number"
}

Loops

for (a in 1..5) {
    print "${a} "
}  // 1 2 3 4 5

for (i in [0, 1, 2]) {
    print "${i} "
} // 0 1 2

def map = [aaa: 1, bbb: 2, ccc: 3]

for (e in map) {
    println "${e.key} : ${e.value}"
}

1.upto(5) { print "${it} " } // 1 2 3 4 5

5.times { print "${it} " }  // 0 1 2 3 4

1.step(10, 2) { print "${it} " } // 1 3 5 7 9

Exception Handling

try {
    int i = 1 / 0
} catch (Exception e) {
    println e.getCause()
    println e.getMessage()
    e.printStackTrace()
} finally {
    println "finally"
}

String

String name1 = "john"
def name2 = "Tom"

def name = "john"
def message1 = "Hi ${name}"
def message2 = "Hi $name"
def message3 = "Hi ".concat(name)

def name = "john"

println name[1]  // o
println name[-2]  // h
println name[0..2]  // joh
println name[3..1]  // nho
println name[0,2,3]  // jhn

def name = "john"

println name.substring(2)
println name.subSequence(0, 2)

def message = "This is a groovy class"

println message.split(" ")  // ["This", "is", "a", "groovy", "class"]
println message-("groovy ")  // "This is a class"
println message.toList()
println "groovy " * 3
println /Hi "john"/

def name = "john"

println /Hi "${john}"/
println $/Hi "${john}"/$

Methods

def add(int a=0, int b=0) {
  return a + b;
}

println add()

Closures

def closure = { name -> println "Hi ${name}" }

closure.call("John")
closure("Tom")

def list = ["A", "B", "C"]
def map = [
  "name": "john",
  "age": 21
]

println list.each{ it }
println map.each{ it }

def list = [0, 1, 2]

println list.find { it == 1 }
println list.findAll { it >= 1 }
println list.any { it >= 1 }  // true
println list.every { it >= 1 }  // false
println list.collect { it * 2 }

Lists

def list = ["A", "B", "C", "D"]

println list[0..2]
println list[3..1]

def list = []

list.add(1)
list<<2
list = list + [3, 4]
list = list.plus([5, 6])
list = list.minus([5, 6])
list = list - [3, 4]
list = list.reverse()
list = list.sort()

println 1 in list  // true

Maps

def employee = [
  name: "John",
  age: 20
]

def newEmployee = employee.clone()

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

employee.eachWithIndex { key, value, index ->
  println "${index} ${key} ${value}"
}

Ranges

def range = 1..10

println range  // 1..10
println range.size()  // 10
println range.getFrom()  // 1
println range.getTo()  // 10
println range.from  // 1
println range.to  // 10
println range[1] // 2
println range.isReverse()  // false
println range intanceof java.util.List  // true

def range = 1..10
def subRange = range.subList(3, 7)

println subRange.from  // 4
println subRange.to  // 7

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

Read File

File file = new File("test2.groovy")

println file.text
println file.collect { it }
println file as String[]
println file.readLines()
println file.bytes

new File("test2.groovy").eachLine { line, lineNo ->
    println "${lineNo} | line : ${line}"
}

def line = ""

new File("test2.groovy").withReader { reader ->
    while ((line = reader.readLine()) != null) {
        println line
    }
}

new File(".").eachFile { file ->
    println file.getAbsolutePath()
}

// 하위 디렉토리까지 탐색
new File(".").eachFileRecurse { file ->
    println file.getAbsolutePath()
}

new File("test3.groovy") << new File("test2.groovy").text

Write File

File file = new File("test.txt")

file.write("Hello World")
file.text = "Hello World 3"

file.withWriter { writer ->
    writer.writeLine("Hello World 4")
}

file.bytes = []

File file = new File("test.txt")

file << "Hello World 1"
file.append("Hello World 2")

Regex

def message = "This is Groovy"
def regex = /(?:[^Groovy]*)/
def match = message =~ regex

println match[0]

Class

class Car {
  int color = 0

  def getColor() {
    return color
  }

  abstract def getName()
}

class Bmw extends Car {
  @Override
  public Object getName() {
    return "BMW"
  }
}

interface Car {
  def startEngine()
  def stopEngine()
}

class Bmw implements Car {
  @Override
  public Object startEngine() {
    return null
  }

  @Override
  public Object stopEngine() {
    return null
  }
}

class Foo {
  Foo(Integer x) {
    println 'my constructor was called'
  }

  Foo() {}

  def a
  def b
}

new Foo(1)

foo = new Foo(a: '1', b: '2')

assert foo.a == "1"

Json

def json = JsonOutput.toJson([
	student: [
		name: "john",
		age: 25
	]
])

println json
println JsonOutput.prettyPrint(json)

참고

• https://youtube.com/playlist?list=PLhW3qG5bs-L8T6v6DgsZo93DgYDmOF9u4