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421 lines
8.5 KiB
Markdown
421 lines
8.5 KiB
Markdown
---
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language: Groovy
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filename: learngroovy-cn.groovy
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contributors:
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- ["Roberto Pérez Alcolea", "http://github.com/rpalcolea"]
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translators:
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- ["Todd Gao", "http://github.com/7c00"]
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lang: zh-cn
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---
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Groovy - Java平台的动态语言。[了解更多。](http://www.groovy-lang.org/)
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```groovy
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/*
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安装：
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1) 安装 GVM - http://gvmtool.net/
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2) 安装 Groovy： gvm install groovy
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3) 启动 groovy 控制台，键入： groovyConsole
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*/
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// 双斜线开始的是单行注释
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/*
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像这样的是多行注释
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*/
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// Hello World
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println "Hello world!"
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/*
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变量：
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可以给变量赋值，以便稍后使用
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*/
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def x = 1
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println x
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x = new java.util.Date()
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println x
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x = -3.1499392
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println x
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x = false
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println x
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x = "Groovy!"
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println x
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/*
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集合和映射
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*/
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//创建一个空的列表
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def technologies = []
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/*** 往列表中增加一个元素 ***/
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// 和Java一样
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technologies.add("Grails")
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// 左移添加，返回该列表
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technologies << "Groovy"
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// 增加多个元素
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technologies.addAll(["Gradle","Griffon"])
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/*** 从列表中删除元素 ***/
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// 和Java一样
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technologies.remove("Griffon")
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// 减号也行
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technologies = technologies - 'Grails'
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/*** 遍历列表 ***/
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// 遍历列表中的元素
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technologies.each { println "Technology: $it"}
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technologies.eachWithIndex { it, i -> println "$i: $it"}
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/*** 检查列表内容 ***/
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//判断列表是否包含某元素，返回boolean
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contained = technologies.contains( 'Groovy' )
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// 或
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contained = 'Groovy' in technologies
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// 检查多个元素
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technologies.containsAll(['Groovy','Grails'])
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/*** 列表排序 ***/
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// 排序列表（修改原列表）
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technologies.sort()
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// 要想不修改原列表，可以这样：
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sortedTechnologies = technologies.sort( false )
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/*** 列表操作 ***/
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//替换列表元素
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Collections.replaceAll(technologies, 'Gradle', 'gradle')
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//打乱列表
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Collections.shuffle(technologies, new Random())
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//清空列表
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technologies.clear()
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//创建空的映射
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def devMap = [:]
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//增加值
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devMap = ['name':'Roberto', 'framework':'Grails', 'language':'Groovy']
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devMap.put('lastName','Perez')
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//遍历映射元素
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devMap.each { println "$it.key: $it.value" }
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devMap.eachWithIndex { it, i -> println "$i: $it"}
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//判断映射是否包含某键
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assert devMap.containsKey('name')
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//判断映射是否包含某值
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assert devMap.containsValue('Roberto')
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//取得映射所有的键
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println devMap.keySet()
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//取得映射所有的值
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println devMap.values()
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/*
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Groovy Beans
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GroovyBeans 是 JavaBeans，但使用了更简单的语法
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Groovy 被编译为字节码时，遵循下列规则。
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* 如果一个名字声明时带有访问修饰符（public, private, 或者 protected），
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则会生成一个字段（field）。
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* 名字声明时没有访问修饰符，则会生成一个带有public getter和setter的
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private字段，即属性（property）。
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* 如果一个属性声明为final，则会创建一个final的private字段，但不会生成setter。
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* 可以声明一个属性的同时定义自己的getter和setter。
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* 可以声明具有相同名字的属性和字段，该属性会使用该字段。
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* 如果要定义private或protected属性，必须提供声明为private或protected的getter
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和setter。
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* 如果使用显式或隐式的 this（例如 this.foo, 或者 foo）访问类的在编译时定义的属性，
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Groovy会直接访问对应字段，而不是使用getter或者setter
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* 如果使用显式或隐式的 foo 访问一个不存在的属性，Groovy会通过元类（meta class）
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访问它，这可能导致运行时错误。
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*/
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class Foo {
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// 只读属性
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final String name = "Roberto"
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// 只读属性，有public getter和protected setter
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String language
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protected void setLanguage(String language) { this.language = language }
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// 动态类型属性
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def lastName
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}
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/*
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逻辑分支和循环
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*/
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//Groovy支持常见的if - else语法
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def x = 3
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if(x==1) {
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println "One"
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} else if(x==2) {
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println "Two"
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} else {
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println "X greater than Two"
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}
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//Groovy也支持三元运算符
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def y = 10
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def x = (y > 1) ? "worked" : "failed"
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assert x == "worked"
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//for循环
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//使用区间（range）遍历
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def x = 0
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for (i in 0 .. 30) {
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x += i
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}
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//遍历列表
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x = 0
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for( i in [5,3,2,1] ) {
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x += i
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}
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//遍历数组
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array = (0..20).toArray()
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x = 0
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for (i in array) {
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x += i
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}
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//遍历映射
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def map = ['name':'Roberto', 'framework':'Grails', 'language':'Groovy']
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x = 0
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for ( e in map ) {
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x += e.value
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}
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/*
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运算符
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在Groovy中以下常用运算符支持重载：
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http://www.groovy-lang.org/operators.html#Operator-Overloading
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实用的groovy运算符
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*/
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//展开（spread）运算符：对聚合对象的所有元素施加操作
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def technologies = ['Groovy','Grails','Gradle']
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technologies*.toUpperCase() // 相当于 technologies.collect { it?.toUpperCase() }
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//安全导航（safe navigation）运算符：用来避免NullPointerException
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def user = User.get(1)
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def username = user?.username
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/*
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闭包
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Groovy闭包好比代码块或者方法指针，它是一段代码定义，可以以后执行。
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更多信息见：http://www.groovy-lang.org/closures.html
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*/
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//例子：
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def clos = { println "Hello World!" }
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println "Executing the Closure:"
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clos()
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//传参数给闭包
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def sum = { a, b -> println a+b }
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sum(2,4)
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//闭包可以引用参数列表以外的变量
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def x = 5
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def multiplyBy = { num -> num * x }
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println multiplyBy(10)
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// 只有一个参数的闭包可以省略参数的定义
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def clos = { print it }
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clos( "hi" )
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/*
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Groovy可以记忆闭包结果 [1][2][3]
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*/
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def cl = {a, b ->
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sleep(3000) // 模拟费时操作
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a + b
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}
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mem = cl.memoize()
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def callClosure(a, b) {
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def start = System.currentTimeMillis()
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mem(a, b)
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println "Inputs(a = $a, b = $b) - took ${System.currentTimeMillis() - start} msecs."
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}
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callClosure(1, 2)
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callClosure(1, 2)
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callClosure(2, 3)
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callClosure(2, 3)
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callClosure(3, 4)
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callClosure(3, 4)
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callClosure(1, 2)
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callClosure(2, 3)
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callClosure(3, 4)
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/*
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Expando
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Expando类是一种动态bean类，可以给它的实例添加属性和添加闭包作为方法
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http://mrhaki.blogspot.mx/2009/10/groovy-goodness-expando-as-dynamic-bean.html
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*/
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def user = new Expando(name:"Roberto")
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assert 'Roberto' == user.name
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user.lastName = 'Pérez'
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assert 'Pérez' == user.lastName
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user.showInfo = { out ->
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out << "Name: $name"
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out << ", Last name: $lastName"
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}
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def sw = new StringWriter()
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println user.showInfo(sw)
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/*
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元编程(MOP)
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*/
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//使用ExpandoMetaClass增加行为
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String.metaClass.testAdd = {
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println "we added this"
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}
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String x = "test"
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x?.testAdd()
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//拦截方法调用
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class Test implements GroovyInterceptable {
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def sum(Integer x, Integer y) { x + y }
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def invokeMethod(String name, args) {
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System.out.println "Invoke method $name with args: $args"
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}
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}
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def test = new Test()
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test?.sum(2,3)
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test?.multiply(2,3)
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//Groovy支持propertyMissing，来处理属性解析尝试
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class Foo {
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def propertyMissing(String name) { name }
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}
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def f = new Foo()
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assertEquals "boo", f.boo
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/*
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类型检查和静态编译
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Groovy天生是并将永远是一门动态语言，但也支持类型检查和静态编译
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更多： http://www.infoq.com/articles/new-groovy-20
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*/
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//类型检查
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import groovy.transform.TypeChecked
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void testMethod() {}
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@TypeChecked
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void test() {
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testMeethod()
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def name = "Roberto"
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println naameee
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}
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//另一例子
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import groovy.transform.TypeChecked
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@TypeChecked
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Integer test() {
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Integer num = "1"
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Integer[] numbers = [1,2,3,4]
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Date date = numbers[1]
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return "Test"
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}
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//静态编译例子
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import groovy.transform.CompileStatic
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@CompileStatic
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int sum(int x, int y) {
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x + y
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}
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assert sum(2,5) == 7
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```
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## 进阶资源
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[Groovy文档](http://www.groovy-lang.org/documentation.html)
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[Groovy web console](http://groovyconsole.appspot.com/)
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加入[Groovy用户组](http://www.groovy-lang.org/usergroups.html)
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## 图书
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* [Groovy Goodness] (https://leanpub.com/groovy-goodness-notebook)
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* [Groovy in Action] (http://manning.com/koenig2/)
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* [Programming Groovy 2: Dynamic Productivity for the Java Developer] (http://shop.oreilly.com/product/9781937785307.do)
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[1] http://roshandawrani.wordpress.com/2010/10/18/groovy-new-feature-closures-can-now-memorize-their-results/
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[2] http://www.solutionsiq.com/resources/agileiq-blog/bid/72880/Programming-with-Groovy-Trampoline-and-Memoize
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[3] http://mrhaki.blogspot.mx/2011/05/groovy-goodness-cache-closure-results.html
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