face recognition java

AVG (score) desc120. Check the results of students who are between 3rd and 6th in the following courses:--[Student id],[student name], Enterprise management, Marx, UML, database, average scoreSelect Top 6 max (A.SNO) number, max (b.sname) name,Max (case if CNO = 1 then score end) as Enterprise management,Max (case if CNO = 2 then score end) as Marx,Max (case if CNO = 3 then score end) as UML,Max (case if CNO = 4 then score end) as database,AVG (score) as average scoreFrom SC A, student BWhere A

Java face test questions-generic article 14 139. What is generics in Java? What are the benefits of using generics? Generics are a new feature of the Java SE 1.5, the essence of which is a parameterized type, which means that the data type being manipulated is specified as a parameter. Benefits: 1. Type safety, provid

copy arrays, so performance must be poor, but the read operation because the object and write operation is not the same object, read between the need to lock, the synchronization between read and write only after writing through a simple "=" To point a reference to a new array object, which hardly takes time, so that the read operation is very safe, suitable for use in multi-threading, never concurrentmodificationexception, So copyonwritearraylist is suitable for scenarios where read operations

code (you need to add or remove some code in the late code, just modify the parent class code)Iii. Steps of Succession:1. Extract the properties and methods from multiple classes to create a parent class2. After subclasses use the extends keyword to complete inheritance, subclass extends parent class3. You can call the code of the parent class in the subclassNote: A single inheritance in Java, only one parent after the extends keywordSubclass access

. When the data increases, it may exceed the number of elements originally defined, and when the data is reduced, the memory is wasted; the array can be accessed directly from the subscript. The ② linked list is dynamically stored and allocated, which can adapt to the dynamic increase or decrease of data, and can easily insert and delete data items. (when inserting and deleting data items in an array, it is tedious to move other data items) The linked list must find the next element based on the

synchronous.HashMap classHashMap and Hashtable are similar, except that HashMap is non-synchronous and allows NULL, which is null value and null key. , but when HashMap is treated as collection (the values () method returns collection), its iterator operation time overhead is proportional to the capacity of HashMap. Therefore, if the performance of the iterative operation is quite important, do not set the initialization capacity of the hashmap too high or load factor too low.Weakhashmap classW

Recently saw a copy of the question, I feel that the writing is also good, although the author only gave the question no answer, but it is not only a question of the same author is a good summary of the Java programmer should have the technical system, hope to be able to first into Java and confused do not know what to learn to guide the studentsOriginal linkFor some reason I'm going to change my job, so tr

1, in the abstract class can write the main method, why?2, in the interface can write the main method, why?3, Java can use static local variables, why?4, Java class variables, instance variables, local variables in the multi-threaded environment is thread-safe, why?5, a Java file can have up to how big, can have a few methods, a few variables, why?6, a SELECT sta

as the value of the object pointing to the address.strings1= "ABCDE" at run time, the JVM first checks if there is a string in the string constant pool that has "ABCDE", assigns a reference to the string to S1 if it exists, creates the object in a constant pool if it does not exist, and assigns a reference to the object to S1. So the S1 and S2 re-compile phase has been determined, pointing to the same address.The strings3= "abc" + "De", in which "abc" and "De" are constants, are processed as "A

class Singleton { Private static Singleton uniqueinstance = null; Public static Singleton instance () { if (uniqueinstance! = null) returnuniqueinstance; synchronized (Singleton. class ){ if (uniqueinstance = = null) Uniqueinstance = new Singleton (); } returnuniqueinstance; } } or write this:[Java] Public class Singleton { Private static Singleton uniqueinstance = null; Public static

architectural partsPage JSP webpage itselfException exceptions for error pages, not capturedBasic architecture of 3.ServletFor:publicclass ServletName extends HttpServlet {publicvoiddoPostthrows ServletException, IOException { } publicvoiddoGetthrows ServletException, IOException { }} 4. Under what circumstances are doget () and DoPost () called?For:The method property in the form tag in the JSP page is called doget () when it is get, and DoPost () is called when it is p

(Inputmismatchexception e) {System.out.println ("The first number is not formatted");num1=0;}try {Num2=in.nextint ();} catch (Inputmismatchexception e) {System.out.println ("The second number is not formatted");num2=0;}System.out.println ("num1-num2=" + (num1-num2));}}3) The custom exception class, when the subtraction operation, when the first number is greater than the second number, throw "minuend can not be less than the", and write a program to test.Import Java.util.Scanner;Definition of M

function explicitly.The garbage collector can only reclaim memory that is used by objects created by the new keyword, and some of the memory that is used in this way (such as calling C + + local methods) is recycled. Then you need to use Finalize (). Because the free () function is required to release memory in C + +, the Java program calls the Finalize () method to free memory when calling C + +.9. List and briefly explain several common garbage col

is final decorated, it means that the class cannot derive a new subclass and cannot be inherited as a parent class. Therefore, a class cannot be declared abstract and is declared final. Declares a variable or method to be final. Can guarantee that they will not be changed when they are in use. It can be initialized in two places: the first is where it is defined, that is, when the final variable is defined, and the second is in the constructor. These two places can only choose one of them, eith

}SYSTEM.OUT.PRINTLN ("y=" + y),//Y or 0, no self-increment}public static void method4 (int x, int y) {if ((x = =) (++y) Gt 0) {//null operation}SYSTEM.OUT.PRINTLN ("y=" + y);//Y becomes 1, since the increase, indicating that although x==33 is not established, but ++y the execution of the!!! }public static void Method5 () {int b = 0x0f;//16 is automatically converted to decimal int c = 0x31;//16 is automatically converted to decimal int d = b c;//bitwise AND operation (computer will eventually

the runtime polymorphism16. What is hibernate lazy loading? Why should I use lazy loading?The so-called lazy loading, is delayed loading or delayed loading.When the amount of data we access is too large, obviously the cache is inappropriate, because the content capacity is limited, in order to reduce the concurrency, reduce the consumption of system resources, we let the data when needed to load, then we use lazy loading.Hibernate provides lazy loading of propertiesA. Lazy loading of entity obj

with a short code. Convert multiple spaces to a space (5 points)String s = "s tr in G";S=s.replaceall ("+", "");7. Using the socket to write a program, the client sends a request to the server side (to send a string), the service side to send feedback information. (10 points)TCP protocolOnline examples many find themselves. Code too long8. Implement Oracle paging queries with SQL statements. (10 points)SELECT * FROM (select ROWNUM rn,t.* from TableName t where T.rn Select * from TableName where

Yes, but even if you write this class, it doesn't work.This issue involves the delegate mechanism of the loader, in the class loader's structure diagram (below),Bootstrap is the top-level parent class, Extclassloader is a subclass of the Bootstrap class, and Extclassloader is also the parent of AppclassloaderHere in java.lang.String, for example, when I use this class, the Java virtual Opportunity loads the bytecode of the Java.lang.String class into

Recently planned to change jobs, also interviewed a few, because not their favorite so refused some (of course, there are people don't want my ...). ）。 During the interview process, it was found that the investigation of senior Java programmers was mainly about two aspects of knowledge and depth. Here are the questions you encounter during the interview process:1 How to prevent duplicate submissions2 How to track a session in Web development3 100,000

the stored record has a value of two, or because it stores a null value;8. After a week, the project manager assigned the task to you, the content of the task is to add a new * * function for an existing module , it is expected that you two days after the completion, but the actual implementation of the process you have completed the task in one day, What do you plan to do for the rest of the day? 9. which project has the greatest harvest in the past work? What is the harvest? What kind of role