Groovy入门(三)——集合类型List
发布时间:2020-12-14 16:44:32 所属栏目:大数据 来源:网络整理
导读:List groovy中的List结合了Java中数组和List的优势,既可以用下标的形式来访问数组中的元素,而且可以动态扩展数组,相当方便! 声明List List有以下三种声明方式 myList =[1,2,3] myList = new ArrayList() 或者 mylinkList = new Linklist(myList); longLi
Listgroovy中的List结合了Java中数组和List的优势,既可以用下标的形式来访问数组中的元素,而且可以动态扩展数组,相当方便! 声明ListList有以下三种声明方式
List可以像普通数组那样通过下标来访问: myList = ['a','b','c','d','e','f']
assert myList[0] == 'a'
assert myList[1..3]==['b','d']
assert myList[1,3,5]==['b','f']
//remove element d to e
myList[3..5] =[]
//反向遍历
assert myList[4..0] =['e','a']
//负数代表从后往前遍历 -1表示最后一个元素
assert myList[-1]=['f']
其他运算符:myList = []
//append a element plus(Object)
myList+='a'
assert myList == ['a']
myList+=['b','c']
//plus(Collection)
assert myList == ['a','c']
myList = []
//leftShit is like append
myList << 'a'<<'b'
//minu(Collection)
assert myList -['b'] == ['a']
//multiply
assert myList*2 == ['a','a','b']
控制结构groovy中的控制结构和Java也非常相似, for循环的结构则跟Python相似 myList =['a','c']
assert myList.isCase('a')
candidate ='a'
switch(candidate){
case myList:
assert true;
break
default:
assert false
}
//intersection filter 取交集
assert ['x','z'].grep(myList) ==['a']
myList = []
//null List is considered false in if statement
if(myList)
assert false
//for 循环迭代List
str =''
for(i in [1,'x',5]){
str += i
}
assert str == '1x5'
List主要方法assert [1,[2,3]].flatten() == [1,2,3]
assert [1,3].intersect([4,1])==[3,1]
assert [1,3].disjoint([4,5,6])
//当做stack来使用
list = [1,3]
popped = list.pop()
assert popped == 3
assert list == [1,2]
list.push(3) //等价于"<<"操作符
assert list ==[1,3]
assert [1,2].reverse() ==[2,1]
assert [3,1,2].sort() == [1,3]
def list =[[1,0],[0,1,2]]
// compare by first element
list = list.sort{a,b->
//<==> 等价于compare方法
a[0]<=>b[0]
}
assert list == [[0,2],[1,0]]
//compare by size
list = list.sort{item-> item.size()}
assert list ==[[1,2]]
list = ['a','c']
// remove by index
list.remove(2)
assert list ==['a','b']
// remove by value
list.remove(b)
assert list == ['a']
list = ['a','c']
list.removeAll(['b','c'])
assert list ==['a']
//tranform list to another
def doubled = [1,3].collect{item->item*2}
assert doubled == [2,4,6]
find every element matching the closure
def odd = [1,3].findAll{item->item%2==1}
assert odd ==[1,3]
//Remove duplicate elements
def x = [1,1]
assert [1] == new HashSet(x).toList()
assert [1] == x.unique()
//Remove null elements
def x = [1,null,1] == x.findAll{it!=null}
assert [1,1] == x.grep{it}
def list = [1,3]
assert list.count(2) ==1
assert list.max() == 3
assert list.min() == 1
def even = list.find{item->item%2==0}
assert even ==2
assert list.every{item->item<5}
assert list.any{item->item<2}
def store =''
list.reverseEach{item->store+=item}
assert store == '321'
assert list.join('-') == '1-2-3'
result = list.inject(0){
clinks,guests->clinks+=guests}
assert result == 0+1+2+3
assert list.sun() == 6
List实战——快速排序def quickSort(list){
if(list.size() <2)
return list
def pivot = list[list.size().intdiv(2)]
def left = list.findAll{item->item<pivot}
def middle = list.findAll {item->item==pivot}
def right = list.findAll{item->item>pivot}
return (quickSort(left)+middle+quickSort(right))
}
assert quickSort([]) == []
assert quickSort([1]) == [1]
assert quickSort([1,2]) == [1,2]
assert quickSort([2,3]) == [1,3]
assert quickSort([1.0f,'a',10,null]) == [null,1.0f,'a']
assert quickSort('Karin and Dierk') == ' DKaadeiiknnrr'.toList()
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