core java interview programs

type, not the instance. Method (SB); You can modify this instance by means of a method, but this variable cannot be modifiedJava memory leaks as the C + + programmers understand memory leaks are defined on Wikipedia as "in computer science, memory leaks can occur if programs do not properly manage memory allocations." In object-oriented programming, this is a memory leak if an object in memory cannot be accessed in the code. "But in

variable is only visible in the method, construction method, or block of statements that declares it; local variables are static variables on the stack that are seldom used except when declared as constants; Static variables are stored in a static storage area. Static variables are created at the beginning of the program and are destroyed at the end of the program. 3,a instanceof Car. ()=. ()= . () = String site = "www.runoob.com"; int len = Site.length (); String1.concat (string2); Objects of

connection is simple and stateless; The HTTPS protocol is a network protocol built by the SSL+HTTP protocol for encrypted transmission and authentication, which is more secure than the HTTP protocol. HTTP uses port 80 by default, HTTPS uses 443 port by default How HTTPS ensures the security of data transmissionHTTPS is actually in the TCP layer and the HTTP layer between the SSL/TLS to secure the upper layer, the main use of symmetric encryption, asymmetric encryption, certificates, an

multithreaded programs, multiple threads are executed concurrently to improve the efficiency of the program, and the CPU does not go idle because a thread needs to wait for resources. Multiple threads share heap memory, so creating multiple threads to perform some tasks is better than creating multiple processes. For example, Servlets is better than CGI because Servlets supports multithreading and CGI does not support it.How does the volatile keyword

As a Java programmer who is often asked in an interview, let me summarize some of the questions that I often don't ask. The difference between 1.HashMap and Hashtable Often asked. Both are classes of the map interface, which enable you to map a unique key to a specific value. HashMap class is not sorted and can have a null key and multiple null values Hashtable, you cannot have null

: Providing SQL, setting variables in SQL, extracting resultset. Application Core Method : Query () update () Callback Interfaces : PreparedStatementCreator, PreparedStatementSetter, ResultSetExtractor, RowMapper There are two ways to get JdbcTemplate in DAO: Give DAO injected jdbctempate: Bean configuration: datasource->jdbctemplate (requires bean factory control)->dao make DAO class Inheritance Jdbcdaosupport: In

Java Internet for interview-Message Queuing-application scenario 1 Asynchronous processing Scene Description: After the user registers, needs to send the registration mail and the registration message. The traditional approach has two kinds of 1 serial ways; 2. Parallel mode. (1) Serial mode: The registration information will be written to the database after the successful, send the registered mail, and t

August 2007 CSDN reading list "click Count": No.1:java Programmer interview Book No.2:javascript Core technology No.3:joel talk about excellent software development method August 2007 CSDN reading list 4-10: CSS Practical manual ajax basic tutorials Joel says software code Encyclopedia (second edition). NET Software Test Automation Road Visual c#2005 Technology

What is Java core and heap DumpJava programs sometimes produce Java core and heap dump files when they run, typically in cases where a Java program encounters a fatal problem.After a fatal problem occurs, the

and so on are provided, and the waiting/notification mode is implemented. Then in lock, a similar pattern is implemented by condition mates. The essence of the implementation is that a condition contains a wait queue, defining multiple condition, and then there are multiple wait queues, which are used in conjunction with the synchronization queues mentioned above. Synchronization queue-Wait queue model refer to: In the above model, calling the await method is equivalent to moving the fi

and then shift the value2 of the value is stored in the complement>>> 0 for high position after right shiftLogical operators:/| can also be used as a logical operator first to determine the previous condition, if False, you do not have to calculate the latter condition|| First determine the previous condition, and if it is true, you do not have to calculate the latter conditionThe "+" operator:Two operand is an addition when the object is a numeric valueIf there is a string, then the connection

Java Core Technology Volume One Java base type Integral type Data Type Number of bytes range of Values Int 4 +_2^4*8-1 Short 2 +_2^2*8-1 Long 8 +_2^8*8-1 Byte 1 -128-127

linkedhashmap maintains a list of double links running on all items. This list of links defines the order of the iterations, which can be either the Insertion Order (Insert-order) or the access order, where the default iteration access order is the insertion order, in which the elements can be traversed in the order in which they were inserted. Based on the characteristics of the Linkedhashmap access order, it is possible to construct an LRU (Least recently used) least recently using a simple

and business. Tell me about the Exception you often encounter in the project. Tell me about the hardest bug you've encountered in the project, how to solve it. Tell me about your deepest impression in the project and how to solve it. What do you think is the problem with your project? Have you ever experienced CPU 100%, how to troubleshoot and resolve Have you ever encountered memory OOM, how to troubleshoot and resolve Tell me about your practice of agile developmen

1. PrefaceRecently, I've seen several interesting questions about the Java Core class string. The string class is how to implement its immutable attributes, and the benefits of being designed to be immutable. Why is it not recommended to use the + sign to form a new string, it is recommended to use StringBuilder or StringBuffer. Flip through some of the online blogs and StackOverflow, comb

At present, multi-core CPU is the mainstream. The multi-core technology can effectively leverage hardware capabilities and improve throughput. For Java programs, concurrent garbage collection can be implemented. However, Java uses multi-