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 – […]

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 […]

如何在Android Studio的GridLayout中使按钮分布于整个网格，主要使用以下几个属性： app:layout_columnWeight=”1″ app:layout_rowWeight=”1″ app:layout_gravity=”fill” 部分XML代码如下： <?xml version=”1.0″ encoding=”utf-8″?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android=”http://schemas.android.com/apk/res/android” xmlns:app=”http://schemas.android.com/apk/res-auto” xmlns:tools=”http://schemas.android.com/tools” android:layout_width=”match_parent” android:layout_height=”match_parent” tools:context=”.MainActivity”> <androidx.gridlayout.widget.GridLayout android:layout_width=”0dp” android:layout_height=”0dp” app:layout_constraintBottom_toBottomOf=”parent” app:layout_constraintLeft_toLeftOf=”parent” app:layout_constraintRight_toRightOf=”parent” app:layout_constraintTop_toTopOf=”parent”> <Button android:id=”@+id/hello” android:layout_width=”wrap_content” android:layout_height=”wrap_content” android:onClick=”buttonTapped” android:text=”Hello” app:layout_column=”0″ app:layout_columnWeight=”1″ app:layout_rowWeight=”1″ app:layout_constraintBottom_toBottomOf=”parent” app:layout_constraintLeft_toLeftOf=”parent” app:layout_constraintRight_toRightOf=”parent” app:layout_constraintTop_toTopOf=”parent” app:layout_gravity=”fill” app:layout_row=”0″ /> …以下省略 效果图如下：