Error: Could not find or load main class问题解决

错误如下: D:>java Hello Error: Could not find or load main class Hello 代码如下: import org.apache.log4j.Logger; import org.apache.log4j.BasicConfigurator; public class Hello { private static final Logger logger = Logger.getLogger(Hello.class); public static void main(String argv[]) { BasicConfigurator.configure(); logger.debug("Hello world."); logger.info("What a beatiful day."); } } Java环境变量设置有问题,没有包括本目录,解决方法一: 在命令行中指定Classpath D:>java -classpath “.;D:\apache-log4j-1.2.16\log4j-1.2.16.ja r” Hello 0 [main] DEBUG Hello – Hello world.

Servlet输出中文到客户端的乱码解决方法

Servlet在客户端中出现乱码是常见现象,参见Servlet中文乱码原因 解决 Get 和 Post 和客户端,以下两行语句要在获取输出流之前执行,才会生效。问题解决。 response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=utf-8"); //以上两行语句要在获取输出流之前执行。才会生效。 PrintWriter out = response.getWriter(); 完整代码: package com.xionghuilin; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class HelloWorld extends HttpServlet { public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException,ServletException { //以下两行语句要在获取输出流之前执行。才会生效。 response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=utf-8"); //以上两行语句要在获取输出流之前执行。才会生效。 PrintWriter out = response.getWriter(); response.setContentType("text/html;charset=UTF-8"); response.setCharacterEncoding("UTF-8"); request.setCharacterEncoding("UTF-8"); response.setHeader("content-type","text/html;charset=UTF-8"); //以下语句无法解决问题,位置不对 //out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">\r\n"); //<%@ page contentType="text/html; charset=UTF-8" language="java" import="java.sql.*" errorPage="" %> //out.write("<%@ page contentType=\"text/html; charset=UTF-8\" language=\"java\" import=\"java.sql.*\" errorPage=\"\" %>\r\n"); out.write("<html>\r\n"); out.write("<head>\r\n"); //以下语句无法解决问题,位置不对 //设定解码方式 //out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=GBK\">\r\n"); //out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">\r\n"); //out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=gb2312\">\r\n"); out.write("<title>该文件放在根目录下</title>\r\n"); out.write("</head>\r\n"); out.write("\r\n"); out.write("<body>\r\n"); out.write("<font size=20>\r\n"); //以下语句无法解决问题,位置不对 //out.print("采用Servlet实现HelloWorld".getBytes("UTF-8")); out.print("采用Servlet实现HelloWorld"); out.write("\r\n"); out.write("</font>\r\n"); out.write("</body>\r\n"); out.write("</html>"); } } Reference Servlet 中文乱码问题及解决方案剖析 Servlet解决中文乱码 Servlet页面中文乱码问题 解决servlet乱码问题 Servlet中文乱码原因 解决 Get 和 Post 和客户端

findViewById返回gridLayout导致异常解决

以下语句导致了程序异常, GridLayout gridLayout = (GridLayout)findViewById(R.id.gridLayout); 参考链接,在XML中定义的gridLayout与在程序中定义的gridLayout不一致,导至了程序异常,改为一致的定义,问题解决。 程序中的定义为: import android.widget.GridLayout; 然而XML中的定义为: androidx.gridlayout.widget.GridLayout 解决方案: 程序改为以下: androidx.gridlayout.widget.GridLayout gridLayout = findViewById(R.id.gridLayout); 额外的问题,layout如果重叠,如何调整不同layout的显示顺序,在Android Studio中的Component Tree里调整先后顺序,就可以调整layout显示的优先级。 Reference App crashing in the part of Grid layout declaration

J2EE SDK installation error:could not find the required version of Java(TM) 2 runtime environment

最近安装64位的J2EE SDK碰到以下问题: could not find the required version of the Java(TM) 2 runtime environment in ‘(null)’ 原因应该是安装包混淆了JRE的安装位置 参考链接,指定JRE位置,解决问题: D:>java_ee_sdk-6u3-jdk7-windows-x64.exe -j “C:\Program Files\Java\jre7” Reference How to fix error: could not find the required version of the Java(TM) 2 runtime environment in ‘(null)’