java programming test questions and answers

See some Java interview questions, ready to do it yourself and try it out.First, the Java Foundation1. Why is the string class final? A string pool is possible only if the string is immutable. The implementation of a string pool can save a lot of heap space at run time, because different string variables point to the same string in the pool. However, if

objects of this class are used in a multithreaded environment, it is best to use StringBuffer. 39. How do I convert a comma-delimited string into an array? Reference: (1) with regular expressions, the code is roughly: ' string[] result = Orgstr.split (","); ' (2) with StringTokenizer, code:StringTokenizer Tokener = StringTokenizer (Orgstr, ",");String[] result = new String[tokener.counttokens ()];int i = 0;while (Tokener.hasnext ()) {result[i++] = Tokener.nexttoken ();}40. 数组有没有length()方法？Strin

Java written test face to finish the first wave-CSDN blog Links: https://blog.csdn.net/shakespeare001/article/details/51151650 directory Java variablesAbout enumerationsAccess control modifierUTF-8 and GBK encoding conversionstrycatchfinally Execution Order problemStatic code block subclass parent class initialization OrderAbout null objects static variables and

simply use an index instead of creating an iterator object. Linklist also creates objects for each inserted element, all of which you have to understand that it also brings additional overhead.Finally, in the book Practical Java, Peter Haggar suggests using a simple array instead of a vector or ArrayList. This is especially true for programs with high efficiency requirements. Because the use of arrays (array) avoids synchronization, additional method

　　As the first Dark Horse technical blog It is necessary to explain the background. The personal understanding of the blog is to be used in communication, in his study, in the exchange of learning to grow together. Let's get down to the chase. This article is mainly to introduce the black horse in the introduction of testing some of the problems (this should not leak the question bank).First analysis of 10 sets of questions, mostly is the basic knowle

size of the chessboard, followed by a number of NXN 0 or 1.Output format:One of three outputs: X O NIL are all uppercase Letters.Input sample: 4 1 0 0 1 0 1 0 0 0 0 1 0 1 0 0 1 Sample Output: X Time limit: 500ms Memory limit: 32000kbImport java.util.Scanner; public class Hello{public static void main (string[] Args) {//TODO auto-generated method Stubscanner in=new Scanner (System . in); int N=in.nextint (); Th

instability or even crashes, The GC mechanism provided by Java can automatically monitor whether an object exceeds the scope to achieve the purpose of automatically reclaiming memory, and the Java language does not provide an explicit way to dispose of the allocated memory.20. Write a singleton mode (Singleton)//第一种 ：饿汉模式public class SingleTon{ private SingleTon(){} //实例化放在静态代码块里可提高程序的执行效率，但也可能占用更大的空

BULK INSERT? What data formats are used for both front and back interaction? How does the JSON data format verify the format correctly? Try ... catch ... With return, finally executed before return or after? How garbage processor GC works, when the GC executes Order of execution of SQL keywords Springmvc How to build the environment? Spring Hibernate? What are the notes for spring? SPRINGMVC's annotations,hibernate annotations? Several states of a thread? What is the difference b

similarities and differences between JSP and servlet?JSP is the extension of servlet technology, is essentially a simple way of servlet, JSP more emphasis on the application of the appearance of expression, compiled is "class servlet." The main difference between Servlets and JSPs is that the application logic of the servlet is in the Java file and is completely detached from the HTML in the presentation layer, whereas the JSP case is that

indicates whether the FETCH statement returns rows from the active set, such as a row is not returned, the value of this property isTrue? (select 1 items)A.%foundB.%notfoundC.%rowcountD.%isopenAnswer: B%found Boolean property, True if the record was last read successfully;%notfound boolean attribute, opposite to%found;%isopen Boolean property that returns TRUE when the cursor is open;%rowcount Numeric property, returns the number of records that have been read from the cursor212. Which clause i

First, the problem description: Xiao Zhang 51 home, parents arranged for him many blind Date girl, set the number of girls is N. The father is responsible for arranging appointments, and each time a random selection of the object of a blind date, the mother is responsible for recording which girls have dated. The blind Date will not end until after a date with all the girls. Parents are arguing these days and there is no verbal communication between them. So the father didn't know that the girl

Java programming example code based on three algorithm questions of quick sorting, java example Overview Quick sorting is an update of the Bubble sorting we have learned before. They all belong to the exchange sorting class and are sorted by continuous comparison and movement. Quick sorting is a very efficient sorting

, right?No. It has the same hash code.46. After an object is passed as a parameter to a method, this method can change the attributes of this object and return the changed result, so is it a value transfer or a reference transfer?Is the value transfer. Java programming language only supports value passing parameters. When an object instance is passed as a parameter to a method, the parameter value is a refe

entire system?2. High concurrency, how our system supports a large number of requests3. How the cluster synchronizes session state4. Principle of Load Balancing5. If there is a particularly large amount of traffic to the database, how to do optimization (db design, dbio,sql optimization, Java optimization)6. If there is a large area of concurrency, on the basis of not increasing the server, how to resolve the server response is not timely problems. "

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. LOG4J uses the log-level mechanism to write out the log output level in order of output levels from low to high.Answer: log4j is divided into off, FATAL, ERROR, WARN, INFO, DEBUG, all or the level you define. LOG4J recommends using only four levels, with the priority from high to low being ERROR, WARN, INFO, DEBUG. By defining the level here, you can control the switch to the appropriate level of log information in your application. For example, if the info level is defined here, the log infor

How to configure a Tomcat data source Method One: 1. Configure the Context.xml files under Tomcat under the Conf, add Connection pool configuration between: Auth= "Container" Type= "Javax.sql.DataSource" Driverclassname= "Oracle.jdbc.driver.OracleDriver" Url= "Jdbc:oracle:thin: @localhost: 1521:mydb" Username= "Bmgis" Password= "Bmgis" Maxactive= "100″ Maxidle= "30″ Maxwait= "10000″/> 2. Configure the Web.xml in your application to join: In the past Tomcat also need to specify the corresp

://blog.csdn.net/garfielder007/article/details/54432322Structure of the 2,java heap and the permanent generation of pairs (renamed to meta-space after Java8)Heap memory is used to hold objects and arrays created by newPermanent generation (to be sorted): http://www.cnblogs.com/paddix/p/5309550.htmlHttps://www.nowcoder.com/questionTerminal/5c3dc3914da548e5b0617f4da9da7488?pos=208orderByHotValue=13, Regular expressionThis is still to see the Novice tuto

**Record some Java written exams, and interview with less certain questions:The difference between 1,string,stringbuffer,stringbuilder2,servlet is a single instance or multi-instance3,hashmap4,hibernate, the three object states of the session5,javascript closure, JS get form There are also sessions in 6,web, where the SessionID is allocated, the session expires when the browser is closed, and SessionID also exists in the client's cookie,When it shuts

Feedback on issues with the 2017 object-oriented Programming (JAVA) section on nine-week learning summary1. Blog not written by: Gao Shuping Gao Junmei Fong Mau Wang Ruiqiang Zong Peng Li Xianglong Ma Lun Mitch Mao Provencale--The number of students who do not submit the blog in time is on the rise, please think about the value of Java Learning Blog, and some of