How to get the epoch timestamp in Java?

In Java, how to get the epoch timestamp, the number of seconds passed since the epoch? In Java, you can get the current time in milliseconds and then calculate the epoch time: long ts = System.currentTimeMillis()/1000; Example: $ wget –quiet https://github.com/albertlatacz/java-repl/releases/download/428/javarepl-428.jar -O /tmp/javarepo-428.jar && java -jar /tmp/javarepo-428.jar Welcome to JavaREPL version 428 (Java HotSpot(TM) 64-Bit […]

Any good Java REPL tool/implementation?

Any good suggestions on a Java REPL implementation like ‘scala’ and ‘python’ or ‘php -a’? The java-repl tool https://github.com/albertlatacz/java-repl/ works nicely for most situations for me. It is released as a .jar. Hence, it is easy to download and run: $ wget –quiet https://github.com/albertlatacz/java-repl/releases/download/428/javarepl-428.jar -O /tmp/javarepo-428.jar && java -jar /tmp/javarepo-428.jar One usage example is as […]

How to install JRE for Chrome on Linux x86-64

How to install JRE for Chrome on Linux x86-64? Use JRE from Oracle on Fedora Linux x86-64 as the example: Download jre from http://java.com/en/download/manual.jsp?locale=en#lin . Select Linux x64. Install it by # yum install jre-7u40-linux-x64.rpm (the downloaded rpm). Make a softlink of the plugin:$ cd ~/.mozilla/plugins/; ln -s /usr/java/jre1.7.0_40/lib/amd64/libnpjp2.so ./ Restart Chrome and browse chrome://plugins/ […]

How to Implement Hibernate Envers in an Application

Technology Hibernate Envers is the frameworks for auditing entities. As the name suggests Hibernate Envers is developed on top of Hibernate, it will on Hibernate and Hibernate implemented JPA. Hibernate Envers provides easy auditing, versioning solution for entity classes. Advantages of Hibernate Envers: Auditing of all mappings defined by JPA specification. Auditing Hibernate specific mappings […]

Java与C++在语言方面上的不同

1,Java抛弃了头文件、预处理机制、goto语句和多维数组。 2,Java不支持指针。 3,Java抛弃了联合体和结构体。 4,Java不支持独立函数。所有函数必须在类中声明。 5,Java不支持多重继承,可以使用接口模拟多重继承。 6,Java不支持运算符重载。 7,Java中布尔型不再用整数来代替。 8,Java中主函数必须有一个字符串类型的参数。 Java抛弃的C++中的这些机制和结构多数都是“危险”的,减少了语言的复杂性,增强了安全性,虽然在一定程度上减少了其灵活性。

JSP Connecting to MySQL

We use tomcat as the container used for instructions in the post. 1) Download the driver mysql-connector-java-*.*.*-bin.jar and put it into WEB-INF/lib/, and remember to restart tomcat. 2) The example code as follows. String driverName="com.mysql.jdbc.Driver"; String userName="username"; String userPasswd="password"; String dbName="dbname"; String tableName="tablename"; String url="jdbc:mysql://localhost/"+dbName+"?user="+userName+"&password="+userPasswd; Class.forName("com.mysql.jdbc.Driver").newInstance(); Connection conn=DriverManager.getConnection(url); Statement statement = conn.createStatement(); String sql="SELECT * […]

Java Calling Native Functions in .DLL on Windows

How to call a function in .dll from Java on Windows is introduced in this post with an example. Platforms used: OS: Microsoft Windows XP [5.1.2600] C to .dll compiler: MS Visual Studio 2008 JDK: java -version java version “1.6.0_05” Java(TM) SE Runtime Environment (build 1.6.0_05-b13) Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode, sharing) […]

Hadoop TeraSort Benchmark

TeraSort is one of Hadoop’s widely used benchmarks. Hadoop’s distribution contains both the input generator and sorting implementations: the TeraGen generates the input and TeraSort conducts the sorting. Here, we provide a short tutorial for using the Hadoop TeraSort benchmark. TeraGen generates random data that can be used as input data for a subsequent running […]