list操作小技巧

逗號分隔的字串轉換為list

list轉換為逗號分隔的字串

list物件排序

list物件去重

list物件分組，組內求和

lis轉map

list刪除

1. 逗號分隔的字串轉換為list

感謝大佬的分享字串以逗號分隔的轉換為list方法

string str =

"a,b,c"
;list
split= arrays.
aslist
(str.
split
(","))
;

string str =

"a, b, c"
;list
splittolist= splitter.on(
",")
.trimresults()
.splittolist
(str)
;

string str =

"a,b,c"
;list
aslist= arrays.
aslist
(stringutils.
split
(str,
",")
);

string str =

"a,b,c"
;list
str =arrays.
aslist
(stringutils.
commadelimitedlisttostringarray
(str)
);

string str =

"a,b,c"
;list
str = stream.
of(str.
split
(","))
.collect
(tolist()
);

2. list轉換為逗號分隔的字串

list

list =
newarraylist()
;list.
add(
"a")
;list.
add(
"b")
; list.
add(
"c")
;string str = joiner.on(
",")
.join
(list)
;

list

list =
newarraylist()
;list.
add(
"a")
;list.
add(
"b")
;list.
add(
"c")
;string str = stringutils.
join
(list.
toarray()
,","
);

list

list =
newarraylist()
;list.
add(
"a")
;list.
add(
"b")
;list.
add(
"c")
;string str = stringutils.
collectiontodelimitedstring
(list,
",")
;

3. list物件排序

collections.

sort
(list,
newcomparator
()})
;

list.

sort
(comparator.
comparing
(countcarddetailvo:
:屬性)
.reversed()
);list.
sort
(comparator.
comparing
(countcarddetailvo:
:屬性)
);

4. list物件去重

set《物件》 personset =

newtreeset
<
>
((o1, o2)
-> o1.
getid()
.compareto
(o2.
getid()
));

list《物件》 unique = list.

stream()
.collect
(collectingandthen
(tocollection((
)->
newtreeset
<
>
(comparinglong
(物件:
:getid)))
, arraylist:
:new))
;

public

static
predicate
distinctbykey
(function<
?super t, object> keyextractor)
list.
stream()
.filter
(distinctbykey
(p -
> p.
getid()
)).collect
(tolist()
);

5. list物件分組，組內求和

map

> collect = list.
stream()
.collect
(collectors.
groupingby
(persondata:
:gettype)
);

map

collect2 = list.
stream()
.collect
(collectors.
groupingby
(persondata:
:gettype,collectors.
summingint
(persondata:
:getage)))
;

6. lis轉map

map

maps = userlist.
stream()
.collect
(collectors.
tomap
(user:
:getid,function.
identity()
));

map

maps = userlist.
stream()
.collect
(collectors.
tomap
(user:
:getid, function.
identity()
,(key1, key2)
-> key2)
);

map

maps = userlist.
stream()
.collect
(collectors.
tomap
(user:
:getid, user:
:getage,
(key1, key2)
-> key2)
);

map

maps = maps.
uniqueindex
(userlist,
newfunction
()})
;

7. lis刪除

iterator

it=list.
iterator()
;while
(it.
hasnext()
)}

list.

removeif
(user -
> user.屬性.
contains(""
));

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