解決Intellij console亂碼問題

開啟Intellij安裝目錄下/bin/idea.exe.vmoptions或idea64.exe.vmoptions
增加-Dfile.encoding=UTF-8

解決在VM中出現sorry, this application cannot run under a Virtual Machine

在VM資料夾下的vmx檔案內加上
monitor_control.restrict_backdoor = "TRUE"
disable_acceleration = "TRUE"

Java常用套件

1.Lombok
自動產生bean的getter和setter
intellij有支援可直接安裝
https://projectlombok.org/

2.POI
匯入匯出Office功能
https://poi.apache.org/

3.FreeMarker
生成網頁或文件或電子郵件原始碼
https://freemarker.apache.org/

4.MyBatis
ORM框架
http://www.mybatis.org/mybatis-3/

5.HiKari
數據連接池
http://brettwooldridge.github.io/HikariCP/

6.jsoup
解析html、xml
https://jsoup.org/

Java小數點格式化

1.BigDecimal

import java.math.BigDecimal;

import java.math.RoundingMode;

BigDecimal bd = new BigDecimal(輸入);

bd = bd.setScale(小數位數, RoundingMode.HALF_UP);

2.DecimalFormat

import java.math.RoundingMode;

import java.text.DecimalFormat;

DecimalFormat df = new DecimalFormat("0.00");

df.setRoundingMode(RoundingMode.HALF_UP);

df.format(輸入);

MySQL參數

wait_timeout
等待非交互式連接的秒數

interactive_timeout
等待交互式連接的秒數
交互式客戶端定義為在mysql_real_connect（）中使用CLIENT_INTERACTIVE選項的客戶端

Java發送Request

URL urlObtainToken = new URL(URL);
HttpURLConnection connectionObtainToken = (HttpURLConnection) urlObtainToken.openConnection();
connectionObtainToken.setRequestMethod("POST");

connectionObtainToken.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(connectionObtainToken.getOutputStream());
writer.write("...");
writer.close();
if (connectionObtainToken.getResponseCode() == HttpURLConnection.HTTP_OK) {}

json原始碼下載與編譯for Java

因為json無提供jar檔，所以必須到官網下載與自行編譯

官網
http://www.json.org/

原始碼
https://github.com/stleary/JSON-java

須自行建立org和json資料夾以做打包


1.開啟命令提示字元

2.cd json資料夾

3.javac ./org/json/*.java

4.jar -cvf json.jar ./org/json/*.class