java

What is the benefit of Dynamic Polymorphism in Java?

由 别说谁变了你拦得住时间么 提交于 2021-02-18 08:47:05
问题 I am studying up on my Java Programming and Object Oriented Programming. I keep getting hung up on what the benefit of Dynamic Polymorphism is? Take a look at my sample program below. Why would I use example 1 over example 2? class SuperHero { private String power = ("Generic Power"); public void useSuperPower() { System.out.println(power); } } class Spiderman extends SuperHero { private String power = ("Web sling!"); public void useSuperPower() { System.out.println(power); } } class

AES use same IV for encryption and decryption

由 馋奶兔 提交于 2021-02-18 08:46:13
问题 I'm having some issues with my code whereby I am not using the same IV for encryption and decryption. I know in order to do this correctly I have to write the IV to my output file before the data however I am struggling implementing this. Could anyone help me with this issue? Edited code code again to show full scope public class TestFileEncryption { private static void mainCrypto(int cipherMode, File inputFile, File outputFile) throws Exception{ //Let the user enter the key they wish to use

How to store secretKey in KeyStore and retrieve it

由 一个人想着一个人 提交于 2021-02-18 08:45:08
问题 I'm currently developing an android application but i'm expecting some issues due to storage and retrieving of a SecretKey into the Keystore This is my code: Here I generate the SecretKey and then save it into KeyStore, and use it to encrypt my data try { KeyStore keyStore=null; keyStore= KeyStore.getInstance(KeyStore.getDefaultType()); char[] passwordKS="network".toCharArray(); SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); sr.setSeed("any data used as random seed".getBytes());

How to export symmetric encryption key?

由 情到浓时终转凉″ 提交于 2021-02-18 08:41:11
问题 I'm trying to implement the javax.crypto encryption between my apps (through intnets). I follow this (accepted answer): https://stackoverflow.com/questions/4319496/how-to-encrypt-and-decrypt-data-in-java .The problem is as I understood I need to have the same SecretKeySpec key in both of my apps in order to encrypt/decrypt the data. I have no idea how to export it (as a String or anything) and then hardcode it in both of my apps. 回答1: You can export a SecretKey using the getEncoded() method.

How to listen new db records through java

由 女生的网名这么多〃 提交于 2021-02-18 08:33:27
问题 Currently I use while(true) and Thread.sleep() for checking for new records in the db and execute java code. Here is an example: public class StartCommands implements Runnable{ private Active_Job activeJob; Runnable execute_command; public StartCommands(){ activeJobs = new Active_Job(); } @Override public void run(){ int jobId = 0; while(true){ //access the db and get one row from the table by the status jobId = activeJobs.get(Status.NEW); if (jobId > 0){ activeJob.updateStatus(Status.INIT);

Is there a way to shorten a java.security.MessageDigest generated value?

由 ぃ、小莉子 提交于 2021-02-18 08:19:24
问题 If I generate a message digest (for a security feature in my app) using this Java code: java.security.MessageDigest saltDigest = MessageDigest.getInstance("SHA-256"); saltDigest.update(UUID.randomUUID().toString().getBytes("UTF-8")); String digest = String.valueOf(Hex.encode(saltDigest.digest())); I end up with a really long string like the following: 29bcf49cbd57bbc41e601b399a93218ef99c6e36bae3598b5a5a64ac66d9c254 Not the nicest thing to pass on a URL! Is there a way to shorten this? 回答1:

kafka实战

由 十年热恋 提交于 2021-02-18 08:16:51
---------------------------------------------------------------------------------------------------- applicationContext - resources.xml <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation ="http://www.springframework.org/schema/beans http: // www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <!-- load properties --> <bean id="propertyConfigurer" class ="com.agu3.kafka.base.PropertyConfigurer"> <property name="locations"> <list> <value>classpath:/common-kafka

Spring Cloud是什么？

由 白昼怎懂夜的黑 提交于 2021-02-18 08:15:49
[学习笔记] 3）Spring Cloud是什么？ 马克-to-win@马克java社区： i）Spring Cloud是一个微服务框架，Spring Cloud基于微服务基础框架Netflix进行了upgrade，同时又能和 Spring Boot开发框架 集成开发。 ii）Sping Cloud是Spring的一个顶级项目。其中包括Spring Boot，Spring Framework，Spring Data，Spring Cloud Netflix等。马克-to-win@马克java社区：Spring Cloud有很多子项目， 其中Spring Cloud Netflix就是其中之一。这个子项目的目的就是：针对多种Netflix组件提供开发工具包，其中包括Eureka（服务注册与服务发现）、 Hystrix（容错管理）、Ribbon（负载均衡）等。 iii）Spring Cloud：也是微服务工具包，提供了在分布式系统的配置管理、服务发现等开发工具包。比如在咱们下面的项目中就有： <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka-server</artifactId> </dependency> 版权声明：本文为转载文章，原文地址

Calculate previous 12 months from given month - SimpleDateFormat

由 女生的网名这么多〃 提交于 2021-02-18 08:15:19
问题 I am trying to get previous 12 month into an arraylist, from the given month(taken from DB). List<String> allDates = new ArrayList<String>(); sqlQuery="select max(date) from Table_Name"; maxDate="Jan-2016"; (Result from Query); To get previous 12 months from maxDate,where i use SimpleDateFormat. I want to calculate the previous 12 months from Given Month (maxDate), not from current month, i tried the following code. // Parsing maxDate to an integer (say Jan-2016 = 0, Feb-2016= 1) Date date =

Exception in thread “main” java.lang.UnsatisfiedLinkError: no jep in java.library.path

由 若如初见. 提交于 2021-02-18 08:13:11
问题 I have 'libjep.so' file after downloading jep and I also had set the environmental variable LD_LIBRARY_PATH in ~./bashrc as shown below: export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib/python2.7/dist-packages/jep/libjep.so as well as in runtime System.load("/usr/local/lib/python2.7/dist-packages/jep/libjep.so"); But when I have the follwing line in my code, Jep jep = new Jep(); It shows the below error: Exception in thread "main" java.lang.UnsatisfiedLinkError: no jep in java.library
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