One: Background
Students that recently in Nanjing, spent about two weeks in order to find a job to support themselves, constantly brushed questions, resume, go to the company interview, has experienced probably have gone back and forth about 9-10 interview , are generally the first written test, interview and then finally the company in charge of the interview, there are outsourcing companies have the manpower outsourcing company, met a lot of people and things, more or less have a variety of feelings inside, the main purpose of writing this blog summarize met face questions, including written questions the interviewer and technical problems, there are many questions that the interviewer to repeat several interviews, some will not meet her, or the answer is not comprehensive, summary record it here later to facilitate their spare time, for they do not understand or grasp the point of knowledge is not strong knowledge points to enhance learning, but also to the same level with their students encourage each other.
II: face questions
java basis:
(1) the difference between abstract classes and interfaces?
a. single class inheritance, multiple interfaces are implemented
b. There abstract class constructor, and the interface is no constructor
. C abstract class can have both abstract methods, which may have non-abstract methods; and the interface only abstract methods
d. abstract class has member variables, only constants interface
The difference (2) static variables and instance variables
Static variables: static variable keywords modified, also known as class variables, belong to the class, does not belong to any object, static variables and only one copy in memory;
Examples of variables: dependent on an instance, you need to create an object before you can access it through the object, static variables allows multiple objects shared memory.
(3) and the reference transmission value is transmitted
The difference (4) ArrayList and the LinkedList, and Vector
(5) Transfer byte character stream
Circulation input character stream InputStreamReader input stream of bytes is achieved by the class constructor function may pass InputStream object
Byte character output stream output stream OutputStreamWriter achieved by constructor can change the incoming class OutputStream object
(6) the difference between String, StringBuffer, StringBuilder's
a. Variable immutable
String: is a modified final, immutable, if the newly generated modified new string object
StringBuffer and StringBuilder: is variable, each operation will be modified to StringBuffer object itself, does not generate a new object
b. Thread is safe
String: thread-safe
StringBuffer: thread-safe, with respect to the StringBuilder plus (synchronized synchronization lock) on the call method, slow efficiency
StringBuilder: thread-safe, if the program is not multi-threaded, use more efficient than StringBuilder StringBuffer
Database mysql:
The difference between (1) union and the union all
remove duplicate data union
union all query all the data, do not remove the duplicate data
(2) where, group by, having the sequence
where group by having
where conditions filter the raw data
Then the data packets with the added condition group by having, aggregate functions can be added after having, where not added to the
Framework:
Request procedure (1) springMVC of
（2）
ps: in perfected. . . . .