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2019最新整理JAVA面试题附答案

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本人免费整理了Java高级资料，涵盖了Java、Redis、MongoDB、MySQL、Zookeeper、Spring Cloud、Dubbo高并发分布式等教程，一共30G，需要自己领取。传送门： https://mp.weixin.qq.com/s/igMojff-bbmQ6irCGO3mqA 包含的模块：本文分为十九个模块，分别是：Java 基础、容器、多线程、反射、对象拷贝、Java Web 、异常、网络、设计模式、Spring/Spring MVC、Spring Boot/Spring Cloud、Hibernate、MyBatis、RabbitMQ、Kafka、Zookeeper、MySQL、Redis、JVM 如下图所示：共包含 208 道面试题，本文的宗旨是为读者朋友们整理一份详实而又权威的面试清单，下面一起进入主题吧。 ==================================================== 一. Java 基础模块 1.JDK 和 JRE 有什么区别？ JDK：Java Development Kit 的简称，Java 开发工具包，提供了 Java 的开发环境和运行环境。 JRE：Java Runtime Environment 的简称，Java 运行环境，为 Java 的运行提供了所需环境。具体来说 JDK 其实包含了

Passing ArrayList<MyObject> Between multiple Activities

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问题 I am trying to pass an ArrayList of Objects between multiple activities in my application. Is it possible to do this using an Intent using the setData() method? 回答1: If you want to send an ArrayList of objects then your class must implement the Parcelable or Serializable interface . See these good tutorials for sending custom object between Activities http://androidideasblog.blogspot.in/2010/02/passing-list-of-objects-between.html http://www.anddev.org/novice-tutorials-f8/simple-tutorial

Passing ArrayList<MyObject> Between multiple Activities

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Passing ArrayList<MyObject> Between multiple Activities

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How does Swift manage Arrays internally?

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问题 I would like to know how Swift managed arrays internally? Apple's language guide only handles usage, but does not elaborate on internal structures. As a Java-developer I am used to looking at "bare" arrays as a very static and fixed data structure. I know that this is not true in Swift. In Swift, other than in Java, you can mutate the length of an array and also perform insert and delete operations. In Java I am used to decide what data structure I want to use (simple arrays, ArrayList,

How to add an object to an ArrayList in Java

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问题 I want to add an object to an ArrayList , but each time I add a new object to an ArrayList with 3 attributes: objt(name, address, contact) , I get an error. import java.util.ArrayList; import java.util.Scanner; public class mainClass { public static void main(String args[]){ Scanner input = new Scanner(System.in); System.out.println("Plz enter Name : "); String name = input.nextLine(); System.out.println("Plz enter Address : "); String address = input.nextLine(); System.out.println("Plz enter

How to split() a delimited string to a List<String>

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问题 I had this code: String[] lineElements; . . . try { using (StreamReader sr = new StreamReader("TestFile.txt")) { String line; while ((line = sr.ReadLine()) != null) { lineElements = line.Split(','); . . . but then thought I should maybe go with a List instead. But this code: List<String> listStrLineElements; . . . try { using (StreamReader sr = new StreamReader("TestFile.txt")) { String line; while ((line = sr.ReadLine()) != null) { listStrLineElements = line.Split(','); . . . ...gives me, "

How to refer to Enclosing class from Inner class?

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问题 I am extending ArrayList to create a custom ArrayList that can be modified using normal ArrayList methods while iterating over it. For this I am also creating an Iterator. public class SynchronizedList<E> extends ArrayList<E> { // Fields here //Constructors and methods here public class SynchronizedListIterator<E> implements Iterator<E> { public int index; private E current; public boolean hasNext() { synchronized (/* reference to enclosing List object */) { //code goes here } return false; }

JPA passing list to IN clause in named native query

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问题 I know I can pass a list to named query in JPA, but how about NamedNativeQuery? I have tried many ways but still can't just pass the list to a NamedNativeQuery. Anyone know how to pass a list to the in clause in NamedNativeQuery? Thank you very much! The NamedNativeQuery is as below: @NamedNativeQuery( name="User.findByUserIdList", query="select u.user_id, u.dob, u.name, u.sex, u.address from user u "+ "where u.user_id in (?userIdList)" ) and it is called like this: List<Object[]> userList =

Java Generic with ArrayList <? extends A> add element

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问题 I have classes A , B , C and D where B extends A , C extends A and D extends A . I have the following ArrayList s each with a few elements in them: ArrayList<B> b; ArrayList<? extends A> mix = b; I intended for the variable mix to contain elements of type B , C or D . I tried to add an element of type C into mix like this: mix.add(anElementOfTypeC); But the IDE doesn't allow me to do so and it says: anElementOfTypeC cannot be converted to CAP#1 by method of invocation conversion where CAP#1