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Java

Java???

???? ?? ???? ???? ??? ???? Java? ???? ??????

???? ?? ???? ???? ??? ???? "java"? ???? ??? ????. ??? 1, "startsWith" ???? ???? ??? ???? ????? ???? ? ?????. ??? 2, "contains" ???(if and only) ???? ??? "char" ? ???? ????? ?? "true"? ?????.

Nov 30, 2019 am 10:55 AM

java ?? ???? ?

== ??? Java?? ??? ??????

Java? "=="? ? ????? ?? ??? ???? ? ???? ?? ??????. ??? ??? ????. ?? ??? ??? ?? ==? ?? ???? ??? ?????. ?? ??? ??? ?? ==? ?? ?? ???? ??? ?????.

Nov 30, 2019 am 10:47 AM

java

IP?? ???? Java ??

Java? ??? "([1-9]|[1-9]\\d|1\\d{2}|2[0-4]\\d|25[0-5]? ???? ???? ??? ? ????. ) (\\.(\\d|[1-9]\\d|1\\d{2}|2[0-4]\\d|25[0-5])){3}" ~ ?? .

Nov 30, 2019 am 10:37 AM

java

Java? ? ???? ?? ??? ???? ??

"map" ???? "key"? ??? ???? "java"? ??? ??? ????. ?? "map" ??? ?????? ?? ??? ?? ???? ?? ??? ???? "java"?? ???? "containsKey"? ?????. api" ????? ???? ??? ??? ???? ???.

Nov 30, 2019 am 10:33 AM

java key ?? ????

Java?? ???? ??? ??? ?? ???

Java? ???? ??????? ??? ?? ??? ??? ? ????. ??? ??? ??? ????? String(str.getBytes(charsetName), "utf-8")? ?????. charsetName? ?? ?? ????? "utf-8"? str? utf-8 ????? ?????.

Nov 30, 2019 am 10:21 AM

java

json?? ???? Java ???

Java? ??? ?? ???? json ???? ??? ??? ? ????. json ?? ???? ?? ????? try..catch? JSONObject.parseObject(String str) ???? ?????. json ?? ???? ?? ?? false? ?????.

Nov 30, 2019 am 10:09 AM

java

Java? if ?? ???? ???? ?? ??? ?? null?? ?????.

"java"? "if" ?? ???? ???? ?? ??? ?? "null"?? ???? ??? ??? ????. ?? ? ???? "null" ???? ??? ?? ??? ??? ? ????? ?????. , ?? ?? "! =" ???? ???? ???? "null"?? ??? ??? ? ????.

Nov 30, 2019 am 09:55 AM

if java null ? ?

Java? ???? ???? ?????.

Java?? ???? ???? ???? ??: 1. ???? ??? ?? isDigit() ??? ???? ?? ??? ???? ?????. 2. ??? "^[-\\+]?[\\d]*$"? ???? ?????. 3. ??? ??? ?????.

Nov 30, 2019 am 09:53 AM

java

Java? ??? ??? ?????.

Java?? ??? ??? ??? ???? ??: 1. Calendar ???? ???? ??? ???? ??? ?????. ? ???? ????? ? ?? ???? 1~7 ??? ??? ?????. ?????. 2. SimpleDateFormat ???? ???? ??? ??? ??? ?????. EEEE ????? ???? ??? ?????.

Nov 30, 2019 am 09:43 AM

java

Java? ??? ????? ???? ???? ?????.

"file" ??? ????? ???? "java" ??? ??? ????. ??? ????? ????? "File" ???? "file.exists" ???? ??? ? ????. ?? "File"? ???? ???. " ???? ??? ? ???? ? ?? ??? ??? ????, "exists" ???? ???? ?? ??? ?? ? ????.

Nov 30, 2019 am 09:40 AM

file java ???? ???? ??

txt ??? ?? Java? ??? ??? ?? ???

Java? txt ??? ?? ? ?? ???? ???? ???. txt ??? ??? ??? ?? ??? ?????. ??????? ?? ??? ??? ??? ?? ???? ???. ??? ??? ?? ? ? ??? ??? ??? ??? ??? ???? ????.

Nov 30, 2019 am 09:32 AM

java

Java?? ??? exe ??? ?? ??

"java"? ??? "exe" ??? ?? ??? ??? ????. ?? "???" ???? ?? ???? ?? ?????? ?? ??? ??? ??? ??? ?? ?? ??? ?? ?? ????? ?????. ????? ?? ??? ?????.

Nov 30, 2019 am 09:22 AM

exe java ??

???? ??? ???? ??? 4?? ?

Java ?????? ? ? ?? ??? ?? ?????. ? ????? FileStreams? ??? ??, FileChannel? ??? ??, Commons IO? ??? ??, Java7? Files ???? ??? ??? ? ?? ?? ?? ??? ?????.

Nov 29, 2019 pm 05:38 PM

java