编程

Why am I getting a Null Pointer Exception from this Java code? [closed]

Closed. This question is off-topic . It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 10 years ago . I have a method ... where I can't find the error: public String getUsernameforID(int id) { String statment =...

How to run a Jobscheduler or a Service every minute wihout stopping?

I'm doing an Android app that requires sending its location frequently, every 1 minute or 2 minutes at the most. For this, I use a JobSchedulerService . I've already managed to make it run more than once every 15 minutes on devices with Android N version by replacing the .setPeriodic() with a...

HTTP事务处理步骤及web应用程序状态跟踪

HTTP协议定义的事务处理的四个步骤: 1、客户端和服务器建立连接; 2、客户端发送HTTP请求; 3、服务器端接收客户端发送的HTTP请求,生成HTTP响应后回发到客户端; 4、服务器关闭连接,客户端解析回发的响应,页面展示。 HTTP协议是 无状态、无连接、遵循请求/响应 模型的TCP/IP协议簇的成员。 那么这里就有一个问题,客户端与服务器建立的连接只针对一个请求/响应;因为无连接的缘故,web容器不能成功辨识来自同一个客户的第二次请求与第一次请求的请求发送者均为同一个客户;仅仅是从容器的角度考虑,每一次请求都来自于一个新客户...

设计模式之代理模式(Java示例)及其在Spring-AOP特性之中的应用

代理模式: 代理模式就是作为需要被代理的类与使用被代理的桥梁,首先代理类去代理需要被代理的对象,在别的对象需要使用到该对象的时候通过代理类而非直接去找被代理的对象。这样就可以在代理类中对被代理的对象进行增强。代理模式分为静态代理与动态代理。 静态代理: 静态就意味着代理对象代理谁在编译时期就确定了,其实现就是通过去实现被代理类的接口然后再通过组合来实现。 例子: 被代理类接口: package com.ustc; public interface Sub { public void doSomething(); } 被代理类: package com.ustc; import java.sql...

PAT-2019年冬季考试-甲级 7-2 Block Reversing (25分) (链表转置)

7-2 Block Reversing (25分) Given a singly linked list L. Let us consider every K nodes as a block (if there are less than K nodes at the end of the list, the rest of the nodes are still considered as a block). Your job is to reverse all the blocks in L. For example, given L as 1→2→3→4→5→6→7→8 and K...

英语

TCP connection reset by peer AverageDload Received fetch ERROR: Can't find a suitable configuration file in this directory or any parent. Are you in the right directory? Supported filenames: docker-compose.yml, docker-compose.yaml Pulling chemical-redis (redis:4.0.10)... Trying to pull repository...