2020 Senior Engineer Android manufacturers face questions consolidation; Java + Performance Tuning + APP + NDK + cross-platform development technology

EDITORIAL;

Recently, many students find manufacturers face questions in the exchange of the group. Just finishing my computer there are in this area, so he made up for everyone to share.

These topics are friends go to Baidu, millet, music television, the US group, 58, cheetahs, 360, Sina, Sohu and other Internet companies first-line interview asked about the subject. Familiar listed in this article will greatly increase the chances of knowledge through the first two rounds of technical interview.

Divided into the following sections:

(1) java face questions

(2) Android interview questions

(3) development of advanced technical questions

(4) the development of cross-platform Hybrid

A, java face questions

Java proficiency is critical, not only large companies will require you to use several api, more it is to familiarize you with the source code implementation principle, or even less than what you know, how to improve, there are a number of algorithms related to java , design patterns, and so on.

(A) java interview the knowledge base

Java difference in the == and equals and hashCode
int, char, how many half and the number of bytes long
The difference between int and integer
Beating the understanding of polymorphism java
String、StringBuffer、StringBuilder区别
What is the inner class? The role of internal class
The difference between abstract classes and interfaces
Meaning abstract class
Scenarios abstract classes and interfaces
Whether abstract class can not have methods and properties?
Meaning interface
Generics in the difference between extends and super
Static methods of the parent class can overridden by subclasses
The difference between processes and threads
The difference between final, finally, finalize the
Serialization way
The difference between Serializable and Parcelable
Whether static properties and static methods can be inherited? It can be rewritten? And why?
Design intent static inner classes
Members of the inner class, understanding the static inner classes, local inner classes and anonymous inner classes, as well as project application
Talk about the understanding of kotlin
And the difference between the local internal closure class
Convert string to integer manner and principle

(B) java-depth source-level interview questions (difficult)

Objects under what circumstances will be disposed of garbage collection?
Talk about common coding?
utf-8 encoding of Chinese accounted for a few bytes; int type a few bytes?
The difference between static and dynamic proxy agent, what the scene to use?
Java's exception system
Talk about your understanding of the analysis and dispatched.
A modification of the object equals method signature, then use a HashMap to store the object instance when the equals method which will call?
What is the mechanism implemented in Java polymorphism is?
How a Java object serialization to a file?
Talk about your understanding of Java reflection
Talk about your understanding of Java annotations
Talk about your understanding of dependency injection
Say something generic principles and examples
Java in String understanding
Why String designed to be immutable?
equal and hashCode methods of the Object class rewrite, and why?

(C) data structure

Introduction to common data structures
Concurrent collections to know what?
Inheritance relationship between the set list and a set of java
And a set of frame collections
And the difference between the container class presentation (containers estimated that many people have not heard the word, Java container can be divided into four main sections: List List, Set collection, Map mapping tools (Iterator iterator, Enumeration enumeration class, Arrays and Collections), concrete can look at this blog Java container class)
The difference between List, Set, Map of
List and Map implementations and storage
The principle of HashMap
HashMap data structure?
Source understanding HashMap
How HashMap put data (from HashMap to explain the source point of view)?
HashMap how handwriting achieve?
The principle of ConcurrentHashMap
Comparison of ArrayMap and HashMap
The principle HashTable
TreeMap specific implementation
The difference between HashMap and HashTable
The difference between HashMap and HashSet
HashSet and HashMap how to determine a set of elements repeat?
Hash collection Set realize how to prevent collisions
The difference between ArrayList and LinkedList, and application scenarios
The difference between arrays and linked lists
Binary tree of depth-first traversal and breadth-first traversal of the specific implementation
Heap structure
The difference between heap and trees
What is the difference between heap and stack in memory is (answer Tip: You can go two ways to answer from the data structure and the actual implementation aspects)?
What is the deep and shallow copy copy
Handwritten list in reverse order codes
Talk about the understanding of tree, B + tree
Talk about the understanding of the map
Judge single chain ring or not?
Flip the list (ie: Flip a single list)
Merge multiple single ordered list (assuming that all incremental)

(D) thread, multi-thread and thread pool

Three ways to turn thread?
The difference between threads and processes?
Why should there be a thread, rather than the single process?
run () and start () method distinction
How to control a method allows concurrent access to the number of threads?
Different in Java and wait seelp methods;
Talk about understanding wait / notify keywords
What causes threads blocked?
How close the thread?
Talk about the method of synchronization in java
How to ensure data consistency?
How to ensure thread safety?
How to implement thread synchronization?
Two processes at the same time asked to write or read, can not be achieved? How to prevent the synchronization process?
Inter-thread operation List
Java objects in the life cycle
Synchronized usage
synchronize principle
Talk to Synchronized keyword, class locks, lock method, reentrant lock understanding
Multi-thread access and the role of static synchronized method
The same class which two synchronized method, the problem of two threads access
volatile principle
Talk about the use of the volatile keyword
To talk about the role of the volatile keyword
Talk about understanding the NIO
The difference between synchronized and volatile keywords
The difference between synchronized and Lock
ReentrantLock, synchronized and volatile Compare
ReentrantLock internal implementation
lock principle
The four necessary conditions for deadlock?
How to avoid deadlocks?
Whether the object class lock and the lock will affect each other?
What is the thread pool, how to use?
Java concurrency, multithreading, thread model
Talk about the understanding of multi-threaded
Multithreading have any questions to pay attention?
Talk about your understanding of concurrent programming and examples
Talk about your understanding of the multi-thread synchronization mechanism?
How to ensure the safety of multi-threaded file read and write?
Multi-threaded HTTP principle
Realization of HTTP

(E) concurrent programming related knowledge (this is a general Android development with less, it is recommended to see more than):

Android developers usually can be done relatively little to concurrent programming, Thread class is often used, but we want to improve themselves, it must not stop at the surface ,, we should go to find out about the thread-related java source code level thing.

Is attached; and Android core Java Advanced Technical Briefs

Two, Android face questions

Android including Android interview questions based on some source code level, these principles and so on. So big companies want to go to the interview, be sure to look at the source and implementation, the framework can be used to try to achieve what he could not handwritten, exercise yourself.

(A) Android basics of points

What are the four components
The life cycle of the four components and simple usage
Communication between Activity
Life cycle in each case Activity
Time to switch the screen anyway, the life cycle in each case Activity
Life-cycle comparison between Activity and Fragment
There Dialog when the life cycle of pressing the Home key on Activity
Which method is bound to be executed when a few jumps between two Activity?
Front switch to the background, then back to the front desk, Activity lifecycle callbacks. Pop-Dialog, the value of life cycle callback method.
Activity Four started contrast mode
Activity in the state save recovery
Life cycle in each case fragment
Fragment state preservation method which is startActivityForResult class, under what circumstances?
Fragment of how to slide?
Way data transfer between the fragment?
Service Binding Activity and how?
How to start your own corresponding Service in an Activity?
service activity and how to exchange data?
Service open the way
Please describe the lifecycle of Service
Talk about your understanding of ContentProvider
Talk about the relationship between ContentProvider, ContentResolver, ContentObserver
Describe understanding of broadcast BroadcastReceiver
Classification broadcast
Way radio use and scenes
How to register and use BroadcastReceiver in the manifest and the code?
Local and global radio broadcasting what is the difference?
BroadcastReceiver, LocalBroadcastReceiver Ku别
AlertDialog, popupWindow, Activity difference
Application Context object and the difference of Activity
Android attribute animation features
How to import external databases?
LinearLayout, RelativeLayout, FrameLayout characteristics and contrast, and describes the use of scenarios.
Talk about the understanding of the interfaces with the callback
Principle callback
Write a callback demo
Introduce SurfView
RecycleView use
The sequence of action, and the difference of the two sequences Android
The difference is
Estimator
Data storage Android

(Ii) Android source code correlation analysis

Android animation framework implementation principle
The difference between the various versions of Android's API
Requestlayout, onlayout, onDraw, DrawChild differences and relations
And the difference between the use invalidate and postInvalidate
Activity-Window-View three different
Talk about the understanding of the Volley
How to Optimize Custom View
How to achieve high-low version of the SDK version api?
Process describes a network request
HttpUrlConnection and okhttp relations
Understanding Bitmap object
looper architecture
Works ActivityThread, AMS, WMS's
How to Customize View model adaptation considerations
Custom View events
AstncTask + HttpClient and AsyncHttpClient What is the difference?
LaunchMode scenarios
AsyncTask How to use?
SpareArray principle
Please tell us how under ContentProvider achieve data sharing?
Several ways to communicate between AndroidService and Activity
What IntentService principle and the role?
Talk about Activity, Intent, Service What is the relationship
The difference between ApplicationContext and ActivityContext
SP is the process of synchronizing it? Is there any way to do sync?
Talk about the use of multi-threading in the Android
Application process and life cycle
View the package size view of how to know when
RecycleView principle
AndroidManifest role and understanding

(C) some principles of common issues

Handler and mechanisms underlying implementation
Handler, Thread and HandlerThread difference
handler sends a message to the child thread, looper how to start?
About Handler, anywhere in the new Handler is what thread?
ThreadLocal principle, to achieve and how to ensure Local property?
Please explain the relationship between a single-threaded model, Message, Handler, Message Queue, Looper's
Describe View event delivery distribution mechanism
Touch event delivery process
Distribution in the event of onTouch and onTouchEvent What is the difference, how to use?
View and ViewGroup which are related to the event distribution callback method
View refresh mechanism
View Drawing Process
Custom Control Principle
View how to provide a custom interface to obtain View property?
Android code the way to achieve WAP network
AsyncTask mechanism
AsyncTask and lack of principle
How do I cancel AsyncTask?
Why can not update the UI in the sub-thread?
What is the reason ANR is produced?
ANR positioning and correction
What oom that?
What has led oom?
What are the solutions to avoid OOM?
Whether Oom can try catch? why?
What Memory leaks are?
What causes a memory leak?
How to prevent the thread memory leaks?
Solution Memory leaks field
Memory leaks and memory overflow difference?
LruCache default cache size
ContentProvider rights management (Answer: separate read and write, access control - accurate to the table level, URL control)
How do I block and abort a message by radio?
Whether the broadcast can request the network?
Broadcast time limit anr is caused by how much?
Computing a view of a nested hierarchy
Activity stack
Android thread has no upper limit?
Thread pool has no upper limit?
What ListView reuse is?
Why Android introduced Parcelable?
There is no attempt to simplify the use of Parcelable?

Some issues (iv) develop common

ListView pictures misalignment problem is how to generate?
Mixed-use development have to understand it?
Which way hybrid developed know? Say their strengths and weaknesses and each usage scenario? (Answer: For example: RN, weex, H5, applets, WPA, and so do some of the front-end Android understanding js etc. is still very good.);
Screen adaptation of the handling skills are what?
Server only receives data interfaces in multi-threaded or multi-process conditions, how to ensure the orderly arrival of data?
Dynamic layout of understanding
How to remove duplicate code?
Draw the general architecture diagram of Android
The difference Recycleview and ListView
ListView image loading deranged principles and solutions
The concept of dynamic authority adaptation scheme, rights group
Why Android system design ContentProvider?
Pull-down status bar is not affecting the life cycle of activity
If you make a network request onStop time, onResume time how to restore?
What Bitmap use when the attention?
Bitmap of recycler ()
The main steps in opening the camera Android
ViewPager usage details how to set up a time to initialize only the current Fragment, others do not initialize?
Click the event was blocked, but want to spread below View, how to operate?
Implementation of micro-channel main page
Message on the principle of micro-channel red dot
CAS presentation (which is Ali Baba's face questions, I do not really understand, can refer to the blog: CAS Introduction)

It is attached; AndroidAPP outline technology system development framework;

Third, the advanced development technical questions

This is about some high-end Android technology companies need to use large, specially put together a document here, I hope everyone can see. These topics a little technical content, you need a good time to look at the point.

(A) Pictures

Comparison gallery
Source Gallery Analysis
Picture frame cache implementation
LRUCache principle
Image loading principle
Stock themselves to achieve, how do?
Glide source parsing
Glide what caching?
How to control the size of the cache memory Glide?

(Ii) networking and security mechanisms

Comparative analysis of the source framework and network
Network requests to design their own framework, how to do?
okhttp source
Network requests caching, okhttp how to deal with the network buffer
10M load a picture from the network, said Caution
TCP three-way handshake and four wave
The difference between TCP and UDP
TCP and UDP applications
HTTP protocol
HTTP1.0 and 2.0 difference
HTTP packet structure
The difference between HTTP and HTTPS and how to implement security
How to verify the legitimacy of the certificate?
Where used in https symmetric encryption, where the use of asymmetric encryption, whether there is knowledge of the encryption algorithm (such as RSA), etc.?
client如何确定自己发送的消息被server收到?
谈谈你对WebSocket的理解
WebSocket与socket的区别
谈谈你对安卓签名的理解。
请解释安卓为啥要加签名机制?
视频加密传输
App 是如何沙箱化，为什么要这么做？
权限管理系统（底层的权限是如何进行 grant 的）？