Groovy用户指南(3)

3、集合

Groovy支持集合、List、Map和数组

（1）Lists

l         下面是创建List的例子，[]表示空List表达式

list = [5, 6, 7, 8]

assert list.get(2) == 7

assert list instanceof java.util.List

emptyList = []

assert emptyList.size() == 0

emptyList.add(5)

assert emptyList.size() == 1

l         每个List表达式都是java.util.List的实现

（2）范围（Ranges）

l         Range允许创建连续值的列表

l         由于Range扩展java.util.List，所以Range可以作为List使用

l         使用..的Range是包括两个边界，使用...的Range只包括开始边界，而不包括结束边界

// an inclusive range

range = 5..8

assert range.size() == 4

assert range.get(2) == 7

assert range instanceof java.util.List

assert range.contains(5)

assert range.contains(8)

// lets use an exclusive range

range = 5...8

assert range.size() == 3

assert range.get(2) == 7

assert range instanceof java.util.List

assert range.contains(5)

assert ! range.contains(8)

l         Range可以用于实现java.lang.Comparable的Java对象

// an inclusive range

range = 'a'..'d'

assert range.size() == 4

assert range.get(2) == 'c'

assert range instanceof java.util.List

assert range.contains('a')

assert range.contains('d')

assert ! range.contains('e')

l         Range可以用于循环遍历

for (i in 1..10) {

  println "Hello ${i}"

}

（3）Maps

l         下面是创建Map的例子，[:]表示空Map表达式

map = ["name":"Gromit", "likes":"cheese", "id":1234]

assert map.get("name") == "Gromit"

assert map.get("id") == 1234

assert map instanceof java.util.Map

emptyMap = [:]

assert emptyMap.size() == 0

emptyMap.put(5, "foo")

assert emptyMap.size() == 1

assert emptyMap.get(5) == "foo"

l         Map可以象beans一样操作，但key值（类似属性名）必须为有效的String标识

map = ["name":"Gromit", "likes":"cheese", "id":1234]

assert map.name == "Gromit"

assert map.id == 1234

emptyMap = [:]

assert emptyMap.size() == 0

emptyMap.foo = 5

assert emptyMap.size() == 1

assert emptyMap.foo == 5

（4）使用下标操作符

l         可以在字符串、Lists、Maps...中使用下标进行索引

text = "nice cheese gromit!"

x = text[2]

assert x == "c"

assert x.class == String

sub = text[5..10]

assert sub == 'cheese'

map = ["name":"Gromit", "likes":"cheese", "id":1234]

assert map['name'] == "Gromit"

list = [10, 11, 12]

answer = list[2]

assert answer == 12

list = 100..200

sub = list[1, 3, 20..25, 33]

assert sub == [101, 103, 120, 121, 122, 123, 124, 125, 133]

l         可以使用下标操作符更新项目

list = ["a", "b", "c"]

list[2] = "d"

list[0] = list[1]

list[3] = 5

assert list == ["b", "b", "d", 5]

l         可以使用负索引从最后开始计数

text = "nice cheese gromit!"

x = text[-1]

assert x == "!"

name = text[-7..-2]

assert name == "gromit"

l         也可以使用向后范围（开始索引大于结束索引），返回的结果是反转的

text = "nice cheese gromit!"

name = text[3..1]

assert name == "eci"