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Groovy 语言快速入门
30分钟groovy快速入门并掌握

特性

• Groovy 可以与 Java 语言无缝对接
• 调用的方法将在运行时被选择
• Groovy非常容易集成在Java环境中，利用其动态性来做规则引擎、流程引擎、动态脚本环境，非常适合那些不不需要经常发布但又经常变更的场景下使用

语法

基础语法

• #!/usr/bin/env groovy

• import java.util.List as jurist

• 字符串: def str = 'abc'

• def str = "i am $name" GString

  • 可以用\来构建多行的字符串，像bash shell中一样
  • 可以使用”“”来构建多行字符串，像scala中一样

• def c = 'a' as char

• list: def numbers = [1, 2, 3]

  • coll.add("Python")
  • coll << "Smalltalk"
  • coll[5] = "Perl"
  • assert coll[1] == "Java"
  • assert "Java" in coll
  • assert numbers + 5 == [1,2,3,4,5]
  • assert numbers - [2,3] == [1,4]
  • assert numbers.join(",") == "1,2,3,4"
  • assert [1,2,3,4,3].count(3) == 2
  • assert ["JAVA", "GROOVY"] == ["Java", "Groovy"]*.toUpperCase()

• array:def numArr = [1, 2, 3] as int[]

• map: def colors = [red: '#FF0000', green: '#00FF00', blue: '#0000FF']

  • colors.red
  • colors['red']

• range: def range = 0..5

  • assert (0..5).collect() == [0, 1, 2, 3, 4, 5]
  • assert ('a'..'d').collect() == ['a','b','c','d']

• def pattern = ~/fo*/

  • assert str =~ pattern

• artist?.toUpperCase() 防止空指针

• 函数的最后语句值不需要return

• == 等价于 Java 中的equals方法

• with

  server.with {
      name = application.name
      status = status
      sessionCount = 3
      start()
      stop()
  }

• 所有类型都能转成布尔值

  • if (name != null && name.length > 0) {} == if(name){}

流程控制

def x = 1.23
def result = ""
switch (x) {
    case "foo": result = "found foo"
        // lets fall through
    case "bar": result += "bar"
    case [4, 5, 6, 'inList']: result = "list"
        break
    case 12..30: result = "range"
        break
    case Integer: result = "integer"
        break
    case Number: result = "number"
        break
    case { it > 3 }: result = "number > 3"
        break
    default: result = "default"
}
assert result == "number"

函数

def add(int a, int b) {
    return a + b
}
//与上面的等价
def add(a, b) {
    a + b
}

闭包

def closure = {
    param -> println param
}
 
closure('hello')
closure.call('hello')
closure 'hello'

类

class Song {
 def name
 def artist
 def genre
}

• Groovy 自动提供一个构造函数，构造函数接受一个名称-值对的映射，这些名称-值对与类的属性相对应。

常用操作

IO

new File('/User/lihengming/test.txt').withReader('UTF-8') { reader ->
   reader.eachLine {
       println it
   }
}

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