core java questions

* Abstract method *} * 3, the implementation of the interface must also be through the subclass, using the keyword implements, and the interface is multi-implementation of * 4, a subclass can inherit the abstract class and implementation interface * 5, an interface cannot inherit an abstract class, but can be To inherit multiple interfaces at the same time through the extends keyword, implement multiple inheritance of interfaces */interface inter1{public static final int age=100;//common global

Scala, inheriting a base class is similar to Java, with a two-point limit, and (1) Overriding the method requires the Override keyword, (2) only the primary constructor can pass parameters to the base class constructor. Markerfactory is a single case, once the definition is complete, its name represents the only instance of the singleton object, and the singleton can be passed to the function as if it were a typical passing instance.

A core feature of the Bean Validation (JSR 303)--java EE 6, which defines a metadata model and API for entity validation. Its default metadata source is annotations, but developers can extend it through an XML descriptor. The Validation API does not rely on a particular application layer or programming model, so that the same set of validations can be shared by all tiers of the application. It also provides

I. The following is a code snippet of the core data cache mechanism implemented by several experts for your reference. For the core code of this snippet, refer to sun's source code implementation. Sun is not open to this code segment. Its functions have been implemented in ArrayBlockingQueue (jdk1.5) and provide open interfaces. If you do not have time to read the following code, you can directly view t

Category: Java technology 2009-08-29 01:03 213 people read reviews (0) favorite report JavaapiswingxmlioJava's core API is very large, which gives developers a lot of convenience, often people have comments, Java makes programmers become silly.But some of the content I think must be mastered, otherwise it can not be skilled use of

-code unit S u+d835 and u+dd6b. (see http://en.wikipedia.org/wiki/UTF-16 for a description of the encoding algorithm.) in Java, the char type describes a code unit in the UTF-16 encoding.Our strong recommendation isn't to use the char type in your programs unless you are actually manipulating UTF-16 cod E units. You is almost always better off treating strings as abstract data types.3.3.4. The Boolean Type The Boolean type has two values, false and Tr

understand the process of solving the problem, and find out what the individual has done, how to do, and what has been harvested. This is the accumulation of experience. The company ultimately needs to contribute to the work of the staff, so the need for experienced people to help solve the problem, then the ability to solve problems and thinking is very important. For students who do not have much experience, such as a new graduate or an intern, then they need a good foundation and some person

This is the first part of a series of advanced Java interview questions. This section discusses Java core issues such as mutable parameters, assertions, garbage collection, initializers, tokens, dates, calendars, and so on. What is a mutable parameter? The purpose of the assertion? When do I use assert

For this code, a lot of netizens are full of questions, first there are many, not careful, did not write the pair class, to compile.Certainly compiled, the pair class is on the first two pages of the other code.And here, the features of generics are written. By several constructors, and the change of parameters, the generic type is explained.Package pair1;public class pairPrivate T first;Private T second;Public Pair () {first = null;second = null;}Pub

Java core technology: an in-depth understanding of abstract classes and interfaces1. General description Abstract classTemplate Method ModeInterface2 abstract class Abstract classes are classes that cannot be instantiated. They are generally designed to inherit from quilt classes to implement abstract methods of parent classes.The biggest difference from a common class is that it cannot be instantiated. You

/public static void Reset () {instance = new Myclassloader (); Classes.clear (); } /** * reinitialization to implement the class specified by the overload/public static void Reset () { instance = new Myclassloader (); Classes.clear (); } In fact, each reset will produce a new ClassLoader instance, which will be collected in all the instances of the class is recycled after all is reclaimed, where the more unrestrained all reset off, after testing has not found a memory overflow p

Let's talk about some questions about the java programmer interview. This blog post is intended for recent graduates and java programmers who have been working for about two or three years. Why do I need to change jobs? This is a broad question. Everyone has an answer. For example: The company is not well-treated, The salary increase does not meet the expected r

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

transmitted data and send packet data to the target computer or network. Transport layer mainly makes the network program communicate, in the network communication, can adopt the TCP protocol, also can adopt the UDP protocol. The application layer is responsible for the protocol of the application, such as HTTP protocol, FTP protocol, etc.20. Describe your understanding of IP address. To enable computers in your network to communicate, you must specify an identification number for each computer

[] getdeclaredannotations ()//returns TRUE if the program element is a specified type annotation adornment, otherwise returns Falseboolean Isannotationpresent (classThe example code that parses our custom annotation MethodInfo above is as follows (Annotationparser.java):public static void Main (string[] args) { try { Class cls = annotationtest.class; For (Method method:cls.getMethods ()) { MethodInfo MethodInfo = method.getannotation (methodinfo.class); if (me

What is a 1.Java set frame? What are some of the advantages of a collection framework? There are collections in each programming language, and the original Java version contains several collection classes: Vector, Stack, Hashtable, and array. With the extensive use of the collection, Java1.2 proposes a collection framework that encompasses all the set interfaces, implementations, and algorithms.

What is a 1.Java set frame? What are some of the advantages of a collection framework? There are collections in each programming language, and the original Java version contains several collection classes: Vector, Stack, Hashtable, and array. With the extensive use of the collection, Java1.2 proposes a collection framework that encompasses all the set interfaces, implementations, and algorithms.

Java interview questions: Implementation of stacks and queues During the interview, stacks and queues are often checked in pairs. This article includes the following stack and queue test content: 1) stack Creation 2) create a queue 3) Two stacks implement one queue 4) two queues implement one stack 5) design the stack containing the min () function. The time complexity required for min, push, pop, and so o

Multicore CPUs are now the mainstream. Using multi-core technology, can effectively play the ability of hardware, improve throughput, for Java programs, can implement concurrent garbage collection. However, the use of multi-core technology in Java also brings some problems, mainly because of multi-threaded shared memor

JAVA concurrencyParallel programming in Java is complicated, and I don't understand it deeply. But recently, due to the parallel training of classifiers, pondering a little, there are errors please correct me. Just a rough introduction.Many problems we use sequential programming can be solved, but some problems if you can use multi-threaded parallel execution of the task of which can greatly improve the tim