Good morning !
It is really my honor to have this opportunity for an interview,
I hope i can make a good performance today. I'm confident that I can succeed.
Now i will introduce myself briefly
I am 26 years old,born in shandong province .
I was graduated from qingdao university. my major is electronic.and i got my bachelor degree after my graduation in the year of 2003.
I spend most of my time on study,i have passed CET4/6 . and i have acquired basic knowledge of my major during my school time.
In July 2003, I began work for a small private company as a technical support engineer in QingDao city.Because I'm capable of more responsibilities, so I decided to change my job.
And in August 2004,I left QingDao to BeiJing and worked for a foreign enterprise as a automation software test engineer.Because I want to change my working environment, I'd like to find a job which is more challenging. Morover Motorola is a global company, so I feel I can gain the most from working in this kind of company ennvironment. That is the reason why I come here to compete for this position.
I think I'm a good team player and I'm a person of great honesty to others. Also I am able to work under great pressure.
That’s all. Thank you for giving me the chance.
三个特性：encapsulation inheritance polymorphism
常见运行时异常：空指针 ，classcastexception,arrayindexoutofboundexception ,illegalargumentexception,numberformatexception
difference between arraylist linkedlist:
difference between hashset treeset
difference between String[] ArrayList<String>
hashcode
java generics
垃圾回收算法
encapsulation inheritance polymorphism
设计模式（design pattern）：
引用
You can find an overview of a lot of design patterns in Wikipedia. It also mentions which patterns are mentioned by GoF. I'll sum them up here and try to assign as much as possible pattern implementations found in both the Java SE and Java EE API's.
Abstract factory (recognizeable by creational methods returning the factory itself which in turn can be used to create another abstract/interface type)
Builder (recognizeable by creational methods returning the instance itself)
Factory method (recognizeable by creational methods returning an implementation of an abstract/interface type)
Prototype (recognizeable by creational methods returning a different instance of itself with the same properties)
Singleton (recognizeable by creational methods returning the same instance (usually of itself) everytime)
Adapter (recognizeable by creational methods taking an instance of different abstract/interface type and returning an implementation of own/another abstract/interface type which decorates/overrides the given instance)
Bridge (recognizeable by creational methods taking an instance of different abstract/interface type and returning an implementation of own abstract/interface type which delegates/uses the given instance)
- None comes to mind yet. A fictive example would be
new LinkedHashMap(LinkedHashSet<K>, List<V>) which returns an unmodifiable linked map which doesn't clone the items, but uses them. The java.util.Collections#newSetFromMap() and singletonXXX() methods however comes close.
Composite (recognizeable by behavioral methods taking an instance of same abstract/interface type into a tree structure)
Decorator (recognizeable by creational methods taking an instance of same abstract/interface type which adds additional behaviour)
Facade (recognizeable by behavioral methods which internally uses instances of different independent abstract/interface types)
Flyweight (recognizeable by creational methods returning a cached instance, a bit the "multiton" idea)
Proxy (recognizeable by creational methods which returns an implementation of given abstract/interface type which in turn delegates/uses a different implementation of given abstract/interface type)
The Wikipedia example is IMHO a bit poor, lazy loading has actually completely nothing to do with the proxy pattern at all.
Chain of responsibility (recognizeable by behavioral methods which (indirectly) invokes the same method inanother implementation of same abstract/interface type in a queue)
Command (recognizeable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been encapsulated by the command implementation during its creation)
Interpreter (recognizeable by behavioral methods returning a structurally different instance/type of the given instance/type; note that parsing/formatting is not part of the pattern, determining the pattern and how to apply it is)
Iterator (recognizeable by behavioral methods sequentially returning instances of a different type from a queue)
Mediator (recognizeable by behavioral methods taking an instance of different abstract/interface type (usually using the command pattern) which delegates/uses the given instance)
Memento (recognizeable by behavioral methods which internally changes the state of the whole instance)
Observer (or Publish/Subscribe) (recognizeable by behavioral methods which invokes a method on an instance of another abstract/interface type, depending on own state)
State (recognizeable by behavioral methods which changes its behaviour depending on the instance's state which can be controlled externally)
Strategy (recognizeable by behavioral methods in an abstract/interface type which invokes a method in an implementation of a different abstract/interface type which has been passed-in as method argument into the strategy implementation)
Template method (recognizeable by behavioral methods which already have a "default" behaviour definied by an abstract type)
Visitor (recognizeable by two different abstract/interface types which has methods definied which takes each theother abstract/interface type; the one actually calls the method of the other and the other executes the desired strategy on it)
|
英文Java面试题
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 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 Synchronization?
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 while 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 Method1 () {
// Appropriate method-related code.
}
E.g. Synchronizing a block of code inside a function:
public 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 vectors, 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 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 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 corresponding 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 Abstract class:
abstract class testAbstractClass {
protected String myString;
public String getMyString() {
return myString;
}
public abstract string anyAbstractFunction();
}
Question: How to define an Interface?
Answer: In Java Interface defines the methods but does not implement them. Interface can include constants. A class that implements the interfaces is bound to implement all the methods defined in Interface.
Emaple of Interface:
public interface sampleInterface {
public void functionOne();
public long CONSTANT_ONE = 1000;
}
Question: Explain the user defined Exceptions?
Answer: User defined Exceptions are the 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 Exception {
// The class simply has to exist to be an exception
}
Question: 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 in JDBC 2.0 Core API:
Scrollable result sets- using new methods in the ResultSet interface allows programmatically move the to particular row or to a position relative to its current position
JDBC 2.0 Core API provides the Batch Updates functionality to the java applications.
Java applications can now use the ResultSet.updateXXX methods.
New data types - interfaces mapping the SQL3 data types
Custom mapping of user-defined types (UTDs)
Miscellaneous features, including performance hints, the use of character streams, full precision for java.math.BigDecimal values, additional security, and support for time zones in date, time, and timestamp values.
Question: Explain garbage collection?
Answer: Garbage collection is one of the most important feature of Java. Garbage collection is also called automatic memory management as JVM automatically removes the unused variables/objects (value is null) from the memory. User program cann't directly free the object from memory, instead it is the job of the garbage collector to automatically free the objects that are no longer referenced by a program. Every class inherits finalize() method from java.lang.Object, the finalize() method is called by garbage collector when it determines no more references to the object exists. In Java, it is good idea to explicitly assign null into a variable when no more in use. I Java on calling System.gc() and Runtime.gc(), JVM tries to recycle the unused objects, but there is no guarantee when all the objects will garbage collected.
Question: How you can force the garbage collection?
Answer: Garbage collection automatic process and can't be forced.
Question: 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: Encapsulation 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 other 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. Polymorphism 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 Polymorphism.
Answer: From a practical programming viewpoint, polymorphism exists in three distinct forms in Java:
Method overloading
Method overriding through inheritance
Method overriding through the Java interface
Question: What are Access Specifiers available in Java?
Answer: Access specifiers are keywords that determines the type of access to the member of a class. These are:
Public
Protected
Private
Defaults
Question: 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 corresponding type.
Following table lists the primitive types and the corresponding wrapper classes:
Primitive Wrapper
boolean java.lang.Boolean
byte java.lang.Byte
char java.lang.Character
double java.lang.Double
float java.lang.Float
int java.lang.Integer
long java.lang.Long
short java.lang.Short
void java.lang.Void
Question: Read the following program:
public class test {
public static void main(String [] args) {
int x = 3;
int y = 1;
if (x = y)
System.out.println("Not equal");
else
System.out.println("Equal");
}
}
What is the result?
A. The output is equal?br> B. The output 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: C
Question: 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. That 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 variables 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 programs 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 declared 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 ?
Answer: instanceof is a operator, not a function while getClass is a method of java.lang.Object class. Consider a condition where we use
if(o.getClass().getName().equals("java.lang.Math")){ }
This method only checks if the classname we have passed is equal to java.lang.Math. The class java.lang.Math is loaded by the bootstrap ClassLoader. This class is an abstract class.This class loader is responsible for loading classes. Every Class object contains a reference to the ClassLoader that defines. getClass() method returns the runtime class of an object. It fetches the java instance of the given fully qualified type name. The code we have written is not necessary, because we should not compare getClass.getName(). The reason behind it is that if the two different class loaders load the same class but for the JVM, it will consider both classes as different classes so, we can't compare their names. It can only gives the implementing class but can't compare a interface, but instanceof operator can.
The instanceof operator compares an object to a specified 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 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 test1 = new Two();
one test2 = new Three();
System.out.println(test1 instanceof one); //true
System.out.println(test2 instanceof one); //true
System.out.println(Test.getClass().equals(test2.getClass())); //false
}
}
* Q1. How could Java classes direct program messages 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:
Stream st = new Stream(new FileOutputStream("output.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, you have to inherit your class from it and Java does not allow multiple inheritance. On the other hand, you can implement multiple interfaces in your class.
* Q3. Why would you use a synchronized block vs. synchronized method?
A. Synchronized blocks place locks for shorter periods than synchronized methods.
* 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).
* 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 subclass's data type, you need to do explicit casting. For example:
Object a; Customer b; b = (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); 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. 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 called once while regular methods could be called many times.
* Q10. Can you call one constructor from another if a class has multiple constructors
A. Yes. Use this() syntax.
* Q11. Explain the usage of Java packages.
A. This is a way to organize files when a project consists of multiple modules. It also 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.
* Q12. If a class is located in a package, what do you need to change in the OS environment to be able to use it?
A. You need to add a directory or a jar file that contains the package directories to the CLASSPATH environment variable. Let's say a class Employee belongs to a package com.xyz.hr; and is located in the file c:\dev\com\xyz\hr\Employee.java. In this case, you'd need to add c:\dev to the variable CLASSPATH. If this class contains the method main(), you could test it from a command prompt window as follows:
c:\>java com.xyz.hr.Employee
* 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.
* Q14. What would you use to compare two String variables - the operator == or the method equals()?
A. I'd use the method equals() to compare the values of the Strings and the == to check if two variables point at the same instance of a String object.
* Q15. Does it matter in what order catch statements for FileNotFoundException and IOExceptipon are written?
A. Yes, it does. The FileNoFoundException is inherited from the IOException. Exception's subclasses have to be caught first.
* 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.
* Q17. What can go wrong if you replace && with & in the following code:
String a=null; if (a!=null && a.length()>10) {...}
A. A single ampersand here would lead to a NullPointerException.
* Q18. What's the main difference between a Vector and an ArrayList
A. Java Vector class is internally synchronized and ArrayList is not.
* Q19. When should the method invokeLater()be used?
A. This method is used to ensure that Swing components are updated through the event-dispatching thread.
* 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 constructor.
For senior-level developers:
** Q21. 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 rule
** Q22. You can create an abstract class that contains only abstract methods. On the other hand, you can create an interface 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.
** Q23. What comes to mind when you hear about a young generation in Java?
A. Garbage collection.
** Q24. What comes to mind when someone mentions a shallow copy in Java?
A. Object cloning.
** Q25. If you're overriding the method equals() of an object, which other method you might also consider?
A. hashCode()
** Q26. You are planning to do an indexed search in a list of objects. Which of the two Java collections should you use:
ArrayList or LinkedList?
A. ArrayList
** 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 use 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 notifyAll(). 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 package access level.
The 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 英文面试题
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 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 immutable
14.how to write a program using sort program.
15 how to write a program using unsort program.
16.what is legacy.
17.what is legacy api
18.what is legacy interface.
19.what is main difference hashmap and hastable
20.what is main difference between arraylist and vector.
21.what is struts framework.
22.what are distributed 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 and functions.
26.what is jdbc.
27.what are type of drivers.
28.what is type 4 driver.
29.how to collect requuirements 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.please draw struts frame wrok.
34.please draw j2ee architecture.
35.please draw mvc-2 architecture.
36.please draw that how design op module.
37.how to find a file on linux.
38.how to configure weblogic8.1 on linux.
39.why you use struts framework in ur project.
40.what is platfrom independent
41.what is awt and swing.
42.what is heavy wieght components.
43.what is feature of weblgoic8.1.
44.why you choose application server on linux and database server on aix.
45.please 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 jsp
50.why choose weblogic8.1 other than any applicationserver.
51.what is water fall model vs sdlc
52.what is use of dataflowdiagrams
53.wha t is ip in ur project.
54.what about reception module
—————————————————————————————————————————————————————————
1. 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 site
3. Question not available
4. Something
5. oops is Object Oriented Programming
6.what is single inheritance.
ans:one class is inherited by only other one class
7.what is multiple inheritance.
ans:One class inheriting more than one class at atime
8.can java support multiple inheritance.
ans:No
9.what is interface.
ans:Interface has only method declarations but no defn
10.what is differenec between abstract class and interface.
ans:In abstract class some methods may contain definition,but in interface every method should be abstract
11.how to u prove that abstrace class cannot instantiate directly.
ans:As they dont have constructor they cant be instantiated
12.what is differenece between string and stringbuffer.
ans:Strings are immutable where as string buffer can be modified
13.what is immutable
ans:Which cant be changed
14.how to write a program using sort program.
15 how to write a program using unsort program.
ans: Both can be done using javascript
This is for Sort
function SelectTextSort(obj) { // sort by text
var N=obj.options.length;
for (var i=0;i<N-1;i++) {
for (var j=i+1;j<N;j++) {
if ( obj.options[i].text > obj.options[j].text ) {
var i1= (obj.options[i].selected == true ) ? true : false
var j1= (obj.options[j].selected == true ) ? true : false
var q1 = obj.options[j].text;
var q2 = obj.options[j].value;
obj.options[j].text = obj.options[i].text;
obj.options[j].value = obj.options[i].value;
obj.options[i].text = q1;
obj.options[i].value = q2;
obj.options[i].selected = (j1 && true ) ? true : false
obj.options[j].selected = (i1 && true ) ? true : false
}
}
}
return true
}
16.what is legacy.
17.what is legacy api
18.what is legacy interface.
ans: legacy is something that is old in terms of technology/ system
19.what is main difference hashmap and hastable
ans:Hash table is synchronised
20.what is main difference between arraylist and vector.
ans:Vector is synchronised
21.what is struts framework.
22.what are distributed techonologies.
distributed technologies means any technology / s/w program that are having many components in multiple environments that interact with each other depending on the functional requirements and design.
23.what is advantage and disadvantage of distributed techonologies.
overdependance on single platform / single language is avoided. Application can be built flexible to meet requirements. Division of labour is possible. Best of all the technologies and platforms can be optimally utilized. Complexity of requirements can be reduced.
25.what is difference between procedure and functions.'
ans:Fuctions can return value ,procedures cant return value
26.what is jdbc.
ans:Connecting to DB from java program requires JDBC
27.what are type of drivers.
type1,2,3,4
29.how to collect requuirements form u r client.
is not a job of a technical person. It is better for a BA to do it.
30.which process use in ur project.
Generally u can say:
Project related process: Analysis, Design, Sign-off Documents, Implementation, Integration, Testing, UAT
Work related process:
Technical Design, Work Allocation, Code Review Checklist, Unit Test Form will be prepared by the Project Lead and given to the developer.
Developer prepares the Unit Test Case
Implements Code, Performs Test
Submits Code through CVS / VSS
Submits documents along with Release Checklist to the tester / leader.
31.what is deployment descriptor.
ans:Which contains the infrnmation like which file to be used
40.what is platfrom independent
ans:A language is said to be platform independent if it can be run on any machine with out modifying code
41.what is awt and swing.
ans:AWT are heavy weight components and swings are light weight components
46.what is major concepts in oops.
ans:Abstraction,polymorphism,encapsulation,inheritance
47.why u choose mvc-2 architecture.
ans:In MVC-2 controller is servlet rather than JSP which makes it efficient
48.what is implicit object.
ans:Implicit objects are a set of Java objects that the JSP Container makes available to developers in each page
49.how many implicit objects in jsp
ans:out,page,session,request,response,application,page context,config
