在groovy中创建Arraylist和Hashmap的不同方法有哪些

Question

我创建了一个如下所示的ArrayList:

def list = new ArrayList()

但是codenarc报告说它像下面一样警告.

ArrayList objects are better instantiated using the form "[] as ArrayList"

有什么更好的实例化集合的方法？

Answer 1

你可以做:

def list = []               // Default is ArrayList
def list = [] as ArrayList
ArrayList list = []

对于HashMap:

HashMap map = [:]
def map = [:] as HashMap

在这种情况下,默认值为LinkedHashMap:

def map = [:] 

Answer 2

典型的是:

def list = []

其他选择包括

def list = new ArrayList()
def list = new ArrayList<Foo>()
List list = new ArrayList()
def list = [] as ArrayList
List list = [] as ArrayList

而且当然:

List<Foo> list = new ArrayList<Foo>();

存在类似的选择HashMap使用[:].

Answer 3

但是codenarc报告说它像下面一样警告.

ArrayList objects are better instantiated using the form "[] as ArrayList"

IMO,这是对Codenarc的不好建议,因为它假定实现类型[]是ArrayList.今天这是真的,但可能并非总是如此.

创建List实现的最简单/最佳/通常方式是:

def list = []

如果可能的话,我会写一些类似的东西

List<String> list = []

只是为了使这个列表应该包含的内容更加明显,即为了代码可读性.如果我想创建一个特定类型的列表,我会实例化一个List"Java方式"

List<String> list = new SomeCustomListImplementation<String>()

但实际上我不记得曾经这样做过.