Java英文面試題經(jīng)典

1、Java-英文面試題-經(jīng)典英文Java面試題Question: What is transient variable?Answer: Transient variable can t be serialize. For example if a variable is declared as transient in a Serializable class and the class is written to an Objectstream, the value of the variable can't be written to the stream instead when

2、the class is retrieved from the ObjectStream the value of the variable becomes null. Question: Name the containers which uses Border Layout as their default layout?Answer: Containers which uses Border Layout as their default are: window, Frame and Dialog classes.Question: What do you understand by S

3、ynchronization?Answer: Synchronization is a process of controlling the access of shared resources by the multiple threads in such a manner that only one thread can access one resource at a time. In non synchronized multithreaded application, it is possible for one thread to modify a shared object wh

4、ile another thread is in the process of using or updating the object's value. Synchronization prevents such type of data corruption.E. g. Synchronizing a function:public synchronized void Methodi () / Appropriate method-related code.)E. g. Synchronizing a block of code inside a function: public

5、myFunction () synchronized (this) / Synchronized code here.)Question: What is Collection API?Answer: The Collection API is a set of classes and interfaces that support operation on collections of objects. These classes and interfaces are more flexible, more powerful, and more regular than the vector

6、s, arrays, and hashtables if effectively replaces.Example of classes: HashSet, HashMap, ArrayList, LinkedList, TreeSet and TreeMap. Example of interfaces: Collection, Set, List and Map.Question: Is Iterator a Class or Interface? What is its use?Answer: Iterator is an interface which is used to step

7、through the elements of a Collection.Question: What is similarities/difference between an Abstract class and Interface?Answer: Differences are as follows:Interfaces provide a form of multiple inheritance. A class can extend only one other class.Interfaces are limited to public methods and constants

8、with no implementation. Abstract classes can have a partial implementation, protected parts, static methods, etc. A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class.Interfaces are slow as it requires extra indirection to find correspon

9、ding method in the actual class. Abstract classes are fast. Similarities:Neither Abstract classes or Interface can be instantiated.Question: How to define an Abstract class? Answer: A class containing abstract method is called Abstract class. An Abstract class can't be instantiated.Example of Ab

10、stract class:abstract class testAbstractClass protected String myString;public String getMyString() return myString; )publicabstractstringanyAbstractFunction();)Question: How to define an Interface?Answer: In Java Interface defines the methods but does not implement them. Interface can include const

11、ants. A class that implements the interfaces is bound to implement all the methods defined in Interface.Emaple of Interface:public interface samplelnterface public void functionOneO ;public long CONSTANTINE = 1000;Question: Explain the user defined Exceptions?Answer: User defined Exceptions are the

12、separate Exception classes defined by the user for specific purposed. An user defined can created by simply sub-classing it to the Exception class. This allows custom exceptions to be generated (using throw) and caught in the same way as normal exceptions. Example:class myCustomException extends Exc

13、eption / The class simply has to exist to be an exceptionQuestion: Explain the new Features of JDBC 2. 0 Core API?Answer: The JDBC 2.0 API includes the complete JDBC API, which includes both core and Optional Package API, and provides inductrial-strength database computing capabilities.New Features

14、in JDBC 2. 0 Core API:Scrollable result sets- using new methods in the ResultSet interface allows programmatical 1 y move the to particular row or to a position relative to its current positionJDBC 2. 0 Core API provides the Batch Updates functionality to the java applications.Java applications can

15、now use the ResultSet. updateXXX methods.New data types - interfaces mapping the SQL3 data typesCustom mapping of user-defined types (UTDs)Question: Explain garbage collection?Question: How you can force the garbage collection?Answer: Garbage collection automatic process and can t be forced.Question

16、: What is OOPS?Answer: OOP is the common abbreviation for Object-Oriented Programming.Question: Describe the principles of OOPS.Answer: There are three main principals of oops which are called Polymorphism, Inheritance and Encapsulation.Question: Explain the Encapsulation principle.Answer: Encapsula

17、tion is a process of binding or wrapping the data and the codes that operates on the data into a single entity. This keeps the data safe from outside interface and misuse. One way to think about encapsulation is as a protective wrapper that prevents code and data from being arbitrarily accessed by o

18、ther code defined outside the wrapper.Question: Explain the Inheritance principle.Answer: Inheritance is the process by which one object acquires the properties of another object.Question: Explain the Polymorphism principle.Answer: The meaning of Polymorphism is something like one name many forms. P

19、olymorphism enables one entity to be used as as general category for different types of actions. The specific action is determined by the exact nature of the situation. The concept of polymorphism can be explained as "one interface, multiple methods”.Question: Explain the different forms of Pol

20、ymorphism.Answer: From a practical programming viewpoint, polymorphism exists in three distinct forms in Java:Method overloadingMethod overriding through inheritance Method overriding through the Java interfaceQuestion: What are Access Specifiers available in Java?Answer: Access specifiers are keywo

21、rds that determines the type of access to the member of a class. These are:PublicProtectedPrivateDefaultsQuestion: Describe the wrapper classes in Java.Answer: Wrapper class is wrapper around a primitive data type. An instance of a wrapper class contains, or wraps, a primitive value of the correspon

22、ding type.Following table lists the primitive types and the corresponding wrapper classes:Primitive WrapperQuestion: Read the following program: public class test public static void main(String 口 args) int x = 3;int y = 1;if (x = y)else )What is the result?A. The output is equal?br> B The output

23、in not Equal?br> C. An error at ” if (x = y)“ causes compilation to fall.D. The program executes but no output is show on console.Answer: CQuestion: what is the class variables ?Answer: When we create a number of objects of the same class, then each object will share a common copy of variables. T

24、hat means that there is only one copy per class, no matter how many objects are created from it. Class variables or static variables are declared with the static keyword in a class, but mind it that it should be declared outside outside a class. These variables are stored in static memory. Class var

25、iables are mostly used for constants, variable that never change its initial value. Static variables are always called by the class name. This variable is created when the program starts i. e. it is created before the instance is created of class by using new operator and gets destroyed when the pro

26、grams stops. The scope of the class variable is same a instance variable. The class variable can be defined anywhere at class level with the keyword static. It initial value is same as instance variable.When the class variable is defined as int then it's initial value is by default zero, when de

27、clared boolean its default value is false and null for object references. Class variables are associated with the class, rather than with any object.Question: What is the difference between the instanceof and getclass, these two are same or not ?The instanceof operator compares an object to a specif

28、ied type. We can use it to test if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface. We should try to use instanceof operator in place of getClass() method. Remember instanceof opeator and getClass are not same. Try this

29、 example, it will help you to better understand the difference between the two.Interface one)Class Two implements one )Class Three implements one )public class Test public static void main(String args) one testl = new Two();one test2 = new Three();* QI. How could Java classes direct program messages

30、 to the system console, but error messages, say to a file?.The class System has a variable out that represents the standard output, and the variable err that represents the standard error device. By default, they both point at the system console. This how the standard output could be re-directed:Str

31、eam st = new Stream (new Fi 1 eOutput Str earn (/zoutput. txt");System. setErr(st); System. setOut(st);* Q2 What's the difference between an interface and an abstract class?A. An abstract class may contain code in method bodies, which is not allowed in an interface. With abstract classes, y

32、ou have to inherit your class from it and Java does not allow multiple inheritance. On the other hand, you can implement multiple interfacesin your class.* Q3. Why would you use a synchronized block vs. synchronized method?A. Synchronized blocks place locks for shorter periods than synchronized meth

33、ods.* Q4. Explain the usage of the keyword transient?A. This keyword indicates that the value of this member variable does not have to be serialized with the object. When the class will be de-serialized, this variable will be initialized with a default value of its data type (i.e. zero for integers)

34、.* Q5. How can you force garbage collection?A. You can't force GC, but could request it by calling System, gc(). JVM does not guarantee that GC will be started immediately.* Q6. How do you know if an explicit object casting is needed?A. If you assign a superclass object to a variable of a subcla

35、ss' s data type, you need to do explicit casting. For example:Object a; Customer b; b 二(Customer) a;When you assign a subclass to a variable having a supeclass type, the casting is performed automatically.* Q7. What，s the difference between the methods sleep () and wait ()A. The code sleep (1000

36、) ; puts thread aside for exactly one second. The code wait (1000), causes a wait of up to one second. A thread could stop waiting earlier if it receives the notify () or notifyAll () call. The method wait () is defined in the class Object and the method sleep() is defined in the class Thread.* Q8.

37、Can you write a Java class that could be used both as an applet as well as an application?A. Yes. Add a main () method to the applet.* Q9. What's the difference between constructors and other methods?A. Constructors must have the same name as the class and can not return a value. They are only c

38、alled once while regular methods could be called many times.* Q10. Can you call one constructor fromanother if a class has multiple constructorsA. Yes. Use this () syntax.1 Qll. Explain the usage of Java packages.A. This is a way to organize files when a project consists of multiple modules. It also

39、 helps resolve naming conflicts when different packages have classes with the same names. Packages access level also allows you to protect data from being used by the non-authorized classes.2 Q12. If a class is located in a package, what do you need to change in the OS environment to be able to use

40、it?* Q13. What's the difference between J2SDK 1.5 and J2SDK 5. 0?A. There's no difference, Sun Microsystems just re-branded this version.3 Q14. What would you use to compare two String variables - the operator = or the method equals ()?A. r d use the method equals () to compare the values of

41、 the Strings and the = to check if two variables point at the same instance of a String object.4 Q15. Does it matter in what order catch statements for FileNotFoundException and lOExceptipon are written?A. Yes, it does. The FileNoFoundException is inherited from the lOException. Exception，ssubclasse

42、s have to be caught first.5 Q16. Can an inner class declared inside of a method access local variables of this method?A. It's possible if these variables are final.6 Q17. What can go wrong if you replace && with & in the following code:String a=null; if (a!=null && a. length

43、() >10)A. A single ampersand here would lead to a NullPointerException.7 Q18. What's the main difference between a Vector and an ArrayListA.Java Vector class is internallysynchronized and ArrayList is not.8 Q19.Whenshould the methodinvokeLater ()be used?A. This method is used to ensure that S

44、wing components are updated through the event-dispatching thread.9 Q20. How can a subclass call a method or a constructor defined in a superclass?A. Use the following syntax: super. myMethod(); To call a constructor of the superclass, just write super (); in the first line of the subclass' s con

45、structor. For senior-level developers:10 Q2L What's the difference between a queue and a stack?A. Stacks works by last-in-first-out rule (LIFO), while queues use the FIFO rule11 Q22 You can create an abstract class that contains only abstract methods. On the other hand, you can create an interfa

46、ce that declares the same methods. So can you use abstract classes instead of interfaces?A. Sometimes. But your class may be a descendent of another class and in this case the interface is your only option.12 Q23. What comes to mind when you hear about a young generation in Java?A. Garbage collectio

47、n.13 Q24. What comes to mind when someone mentions a shallow copy in Java?A. Object cloning.14 Q25. If you，re overriding the method equals() of an object, which other method you might also consider?A. hashCode ()15 Q26. You are planning to do an indexed search in a list of objects. Which of the two

48、Java collections should you use: ArrayList or LinkedList?A. ArrayList16 Q27. How would you make a copy of an entire Java object with its state?A. Have this class implement Cloneable interface and call its method clone().* Q28. How can you minimize the need of garbage collection and make the memory u

49、se more effective?A. Use object pooling and weak object references.* Q29. There are two classes: A and B. The class B need to inform a class A when some important event has happened. What Java technique would you use to implement it?A. If these classes are threads I'd consider notify () or notif

50、yAll (). For regular classes you can use the Observer interface.* Q30. What access level do you need to specify in the class declaration to ensure that only classes from the same directory can access it?A. You do not need to specify any access level, and Java will use a default packageaccess level.T

51、he J2EE questions are coming soon. Stay tuned for Yakov Fain on Live SYS-CON. TV. Ask your questions to Yakov on the air!IBM java英文面試題1. what is oracle.2. what is major differenece oracle8i and oracle9i.4. tell me some thing ur self.5. please tell me about oops.6. what is single inheritance.7. what

52、is multiple inheritance.8. can java support multiple inheritance.9. what is interface.10. what is differenec between abstract class and interface.11. how to u prove that abstrace class cannot instantiate directly.12. what is differenece between string and stringbuffer.13. what is immutable14. how to

53、 write a program using sort program.15 how towrite a program using unsort program.16. what is legacy.17. what is legacy api18. what is legacy interface.19. what is main difference hashmap and hastable20. what is main difference between arraylist and vector.21. what is struts framework.22. what are d

54、istributed techonologies.23. what is advantage and disadvantage of distributed techonologies.24. what is main difference between jsp and servlets.25. what is difference between procedure andfunctions.26. what is jdbc.27. what are type of drivers.28. what is type 4 driver.29. how to collect requuirem

55、ents form u r client.30. which process use in ur project.31. what is deployment descriptor.32. what is heirarchy of files in struts.33. please34. please35. please36. please37. how to38. how todraw struts frame wrok.draw j2ee architecture.draw mvc-2 architecture.draw that how design op module.find a

56、file on linux.configure weblogic8. 1 on ject.40. what41. what42. what43. whatisisisisplatfrom independent awt and swing.heavy wieght components, feature of weblgoic8. 1.39. why you use struts framework in ur44. why you choose application server onlinux and database server on aix.45. please

57、tell me about ur project.46. what is major concepts in oops.47. why u choose mvc-2 architecture.48. what is implicit object.49. how many implicit objects in jsp50. why choose weblogic8. 1 other than any applicationserver.51. what is water fall model vs sdlc52. what is use of dataf1owdiagrams53. wha

58、t is ip in ur project.54. what about reception module1. Oracle is an RDBMS product with DDL and DML from a company called Oracle Inc.2. Difference between 8i and 9i is given in the Oracle site3. Question not available4. Something5. oops is Object Oriented Programming6. what is single inheritance.ans:one class is inherited by only other one class7. what is multiple inheritance.ans:One class inheri