JAVA TEST 1

1. What is Java?

Why was the Java programming language created?

*C. Java was created to produce applications for small

appliances.（1995年Java衍生自smalltalk最初设计应用于电视机顶盒的嵌入式系统，而后在网络层内意外的大获成就）

 

Which of the following programming paradigms

allows a programmer to develop software based on

entities that simulate real world concepts?

*C. Object Oriented Programming（这门语言可以成为C系列语言中最优秀的，既没有像C++一样的过度设计，又良好的参照了Java的特点）

 

Which one of the following Java keywords is

required when declaring the main method that is

the start of a Java application?

*A. static （每个函数中只有一个main函数，其唯一性就需要被static确定）

 

Which of the following is used to create the file

containing the Java instructions?

*D. text editor

 

Which of the following is true of the Java

programming language?

*D. Code is written in small manageable pieces（每个类更像类，而不像C++一样，几乎被公认为是子程序。）

 

Which of the following could possibly cause a

runtime error?

*C. divide by zero （在Java中，有几种运行时错误，按层次）

 

Which of the following provides the correct

definition of an application?

*B. Computer programs that accept data and produce

useful information.

 

Where can you find the BlueJ IDE?

*A. http://www.bluej.org

 

What must all Java applications contain?

*C. a main method

 

Which of the following computer components are

referred to as hardware?

*C. monitor, CPU, and keyboard

 

Which of the following hardware components is

considered to be the brain of a computer?

*A. CPU

 

Which sequence best describes the physical steps

taken to produce a running Java program?

*C. Write the program.

Compile to bytecode.

Run program.

 

Which of the following is an example of a keyword

that is used to specify access?

*B. public（参照了C）

 

Which of the following computer components is

referred to as a peripheral（外设） device?

*D. Mouse

 

How can you supply data immediately to your

program when you invoke it?

*B. By typing it on the command line.

 

Which of the following are used to instruct a program to

perform mathematical calculations or a test of data?

*D. operators（运算操作符）

 

Which of the following memory types is known as

volatile memory?

*C. RAM

 

Which of the following programming paradigms

requires a programmer to use a divide and conquer

approach to software development?

*D. Procedural Programming

（Procedural programming can sometimes be used as a synonym for imperative programming (specifying the steps the program must take to reach the desired state), but can also refer (as in this article) to a programming paradigm, derived from structured programming, based upon the concept of the procedure call.）

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What is the extension of a Java bytecode file?

*A. .class

What are the tools: javac, appletviewer, javadoc,

and jar a part of?

*B. J2SDK

Which of the following is the machine independent

part used in the execution of a Java program?

*A. bytecode

Why do humans need high-level programming

languages?

*B. Computers process everything in binary and all

information must be converted to binary.

Which of the following programming paradigms do

the Java programming language use?

*B. Object Oriented

Which of the following JDK utility programs is used

to compile a Java source code file into bytecode?

*C. javac

Which of the following uses the correct syntax for a

main() method that starts a Java application?

*C. public static void main(String args[])

2. Object-Oriented Programming

Which of the following terms describes the process

of hiding information in an object?

*A. Encapsulation 封装

Which of the following terms refers to a method

that is used to retrieve data from an object?

*B. Accessor 检索数据 —》访问器

Which of the following is not a compartment of the

Rectangle class symbol?

*C. Instance variables

What does a constructor method do?

*D. It specifies the data values an object will store upon

creation.（产生数据值）

What is "object think"?

*B. A term used to describe how a programmer should

approach the problem specifications.

What is the name of the method that contains the

instructions for cleanup before an object is

destroyed?

*A. Finalizer（Finally类永远是程序最后执行的，这是虚拟机的垃圾回收规定的，我们可以复写，但是默认总存在）

What is a class?

*D. a blueprint or specification of an object

What is the name of the Java library of classes?

*A. API( Application Programming Interface )

Which of the following words is a keyword from the

Java language?

*D. private

What is the best group of methods for a bank

savings account object?

*B. get balance, add interest, set balance, get account

number, set account number

What can be represented as an object?

*C. Almost anything can be considered an object.

What does a method signature not provide?

*C. Object type

What is the name of the uniform system of symbols

and terms used to communicate the design of

classes and applications?

*C. UML Unified Modeling Language

What is another name for an object identifier?

*D. Object reference

Task related objects do not contain which of the

following items?

*B. Client objects

When programmers use "public String getName()",

what are they calling the objects method getName

to do?

*B. Go to the object Name to retrieve data (get…set…)

When using containment and inheritance, what are

two ways that objects can be related?

*B. One object may know about another object and one

object may be part of another object.

Which keyword is used to request that an object be

created?

*C. new

What are mutators(存取器)and constructors called in

object speak?

*D. Accessors

Which of the following choices is an instance of a

class Cycle?

*A. MountainBike

Which of the following terms refers to a method

that accomplishes a non-standard task in a class?

*D. custom method

Which terms are used to describe how an object

knows to do things?

*A. Behaviors and methods

What best describes an accessor?

*D. A method that uses standard ways of retrieving data

from an object.

The term "object attribute" could be best described

by which of the following choices?

*B. Object attributes are what the "object knows."

When using the Java language, a programmer can

accomplish many tasks by what means?

*C. by describing objects and defining how the objects will

interact

3. Java Language Elements

What is the file extension of a Java source file?

*C. .java

What does Java use to delineate a block of

statements?

*A.

What refers to a five faceted storage location in

memory that is used to store data?

*B. Variable

What is available to all objects and methods while

the program is running?

*C. Static storage

Which of the following uses the correct syntax to

instantiate a class?

*D. Point p = new Point();

Which of the following Java commands is used to

create documentation in HTML format from a Java

source code file?

*D. javadoc

Where does Java store data that is required or

referenced by methods?

*B. stack

Which of the following choices is dynamic and the

second fastest storage space?

*D. Stack

-------------------总结上面的几个题--------------------------------

(1)   堆栈。驻留于常规RAM（随机访问存储器）区域，但可通过它的“堆栈指针”获得处理的直接支持。堆栈指针若向下移，会创建新的内存；若向上移，则会释放那些内存。这是一种特别快、特别有效的数据保存方式，仅次于寄存器。创建程序时，Java编译器必须准确地知道堆栈内保存的所有数据的“长度”以及“存在时间”。这是由于它必须生成相应的代码，以便向上和向下移动指针。这一限制无疑影响了程序的灵活性，所以尽管有些Java数据要保存在堆栈里——特别是对象句柄，但Java对象并不放到其中。

(2)   堆。一种常规用途的内存池（也在RAM区域），其中保存了Java对象。和堆栈不同，“内存堆”或“堆”（Heap）最吸引人的地方在于编译器不必知道要从堆里分配多少存储空间，也不必知道存储的数据要在堆里停留多长的时间。因此，用堆保存数据时会得到更大的灵活性。要求创建一个对象时，只需用new命令编制相关的代码即可。执行这些代码时，会在堆里自动进行数据的保存。当然，为达到这种灵活性，必然会付出一定的代价：在堆里分配存储空间时会花掉更长的时间！

(3)   静态存储。这儿的“静态”（Static）是指“位于固定位置”（尽管也在RAM里）。程序运行期间，静态存储的数据将随时等候调用。可用static关键字指出一个对象的特定元素是静态的。但Java对象本身永远都不会置入静态存储空间。

Which of the following terms refers to the usage

rules for symbols and keywords of a language?

*C. syntax

What is the syntax for a multi-line comment in a

Java source file?

*B. /* multi-line

comment */

Which javadoc comment-line option includes the

version information in the generated HTML

documentation?

*D. @version

Which of the following statements about the Java

keywords is true?

*B. they can never be used as identifiers

What is the syntax for a single line comment in a

Java source file?

*A. //

What is the scope of a local variable in a method?

*A. inside the method that declared the variable

What is the purpose of including comments in the

source code?

*A. to communicate with other programmers（and himself as well ）

Which of the following is a special tag that will

insert a frame of text?

*B. @return description

All the following are Java keywords except :

*C. what

What uses memory space in the processor and

provides the fastest access to the data?

*A. Registers

Which of the following integral data types can

store the largest value?

*D. long

Which of the following javadoc special tags is

Synonymous(同意) with the @throws special tag?

*B. @exception

Which symbols are used to enclose javadoc

comments?

*D. /** and */

Which of the following choices is a correct

identifier?

*A. A_Building

What tells the JVM how much memory is required

when storing data?

*D. type of the data

What does Java use as a separator in a method

parameter list?

*C. , (comma)

4. Java Operators and Control

Structures

Which of the following is a valid assignment

statement?

*B. boolean done = true;

What is the result of the following expression?

11000101 ^ 10011001

*C. 01011100（相同0，不同1）

What will happen if a programmer tries to execute

the following code?

byte num;

num = 1 + 3;

*D. the code will not compile because of a type error

Which of the following lines of code will produce a

compilation error?

1. public int test(String x, int n ) {

2. if ( n == 0) return n（没有；）

3. else if (n == 1) {

4. if (x !=null ) return 5;

5. }

6. }

*B. line 2

The modulus operator is used to obtain which of

the following?

*A. the remainder in integer division

Which argument type does the System.out.println()

method require?

*B. It requires a String argument.

What does the '/u' character represent?

*C. The escape sequence to encode a Unicode character

What is casting?

*A. Converting one object type to another type.

Why doesn't this expression throw a null pointer

exception?

Account acct;

if(acct != null && acct.balance > 20.0)

expression is never tested.

*A. The AND is short-circuited so the second relational if(（acct != null ）&& （acct.balance > 20.0）)

Which of the following conversions with primitives

are allowed?

*D. double to float

Which of the following statements best describes a

sequence statement structure?

*B. The flow of execution in a method proceeds from one

statement to the statement following it, in the order they

appear in the source file.

What is the value of c after the following line of

code is executed?

a = 2

b = 4

c = a * b / b + 3 * a;

*B. 8

What is the result of compiling and executing this

code?

public class TestShort{

public static void main(String[] args)

{

short num;

byte x = 2;

byte y = 3;

num = x + y;

}

}

*C. The compile will fail because the + operator sees the

operands as type int.

Which of the following statements regarding shift

operators is true?

*D. When doing the manipulation of bits on primates

larger than 32 bits, the compiler will automatically reduce

the primitives to 32 bits.

What are legal types for the evaluated expression

in a switch statement?

*D. char types

If a class has a private String field to hold an

account number called acctNum, and a public

method called getAcctNum() that returns this

account number String, which line of code would

assign the length of the account number to the variable

lenAcct? The reference to this class is named ba.

*D. lenAcct = ba.getAcctNum().length();

Which of the following operators has the highest

precedence?

*D. parentheses

Is it ever possible to assign the value of variable

with a double value to a float variable?

*A. Yes, but a type cast must be done and there could be

loss of data.（整形截止，再变回整形取值和原来不一样）

What happens when the following lines of code are

compiled and run?

float x;

x = 3.4;

*A. The code will not compile.

Which line of code will correctly assign the value of

"passing" to the String msg if the value of points is

at least 75?

*B. String msg = points >= 75? "passing" : "not passing";

What is the value of x after this statement

executes?

int x = 14/5 * 5;

*B. 10 操作过程即自动发生强制类型转换

The dot operator is used to do which of the

following operations?

*D. The dot operator is used to access non-private

methods or member data of an object.

What is the value of num after this assignment

statement?

double num = 24.0 / 2.0 * 3 + 2;

*C. 38.0

Which of the following answers is the correct way

to declare a Boolean variable named truth?

*A. boolean truth = true;

What is the term is used to describe the data flow

in and out of a Java program?

*B. stream

5. Basics of Defining and Using

Classes

Which best describes the signature of a method?

*B. The signature describes the interface to the method:

the method name, type, and number of arguments

expected.

Which of the following instance variables for a

BankAccount class would be declared as final?

*B. accountNumberID

Which of the following illustrates an overloaded

constructor?

*A. public Person(String name)

public Person(String name, int age)

Which of the following best describes an object's

state?

*C. The current data the object is holding.

What should a variable name start with in order to

comply with improved readability issues?

*B. a lowercase letter

What is the line number in the code listing when

the object x becomes available for destruction?

*D. 15

How does a method keep track of which object is

calling it?

*A. Every instance method has a variable called "this",

which refers to the current object for which the method is

applied.

What can be said about a static class variable?

*B. Any method will see the same variable.

What is required of the method return value(s)?

*B. It must be assignment compatible with the signature.

Which class is considered immutable?

*D. String

When an object of a class is instantiated, what is

needed to work with that object?

*A. a reference to the object

What is a reason for writing a "setter" method?

*B. A "setter" method provides a way to validate data and

maintain consistency among instance variables in a class.

What must all methods have?

*C. a name and return type

What access modifier should be used when

declaring attributes?

*A. private

A math-tutor application is being created that

students will use to practice addition skills. Which

of the following would be defined as an object in

this application?

*C. An addition problem.

What is the proper order for object creation?

*C. memory allocation explicit initialization constructor is executed a reference variable is assigned

What is a reason for writing a "getter" method?

*B. All data in a class must be declared as private and a

"getter" method is the only way to access it.

Which of the following statements is true about the

main() method of an application?

*D. The main() method in a class declared as public is the

starting point for the execution of an application.

How should data that is final and used outside the

object be declared?

*B. public

A static method can only access static class

variables. How does this affect the main() method?

*C. main() cannot access any instance variables of the class

Choose the correct sequence of steps used to

design a class.

*A. Design the attributes and behaviors of the class.

Define the class.

Create an object of the class.

Use the object.

Where is method data stored?

*C. the stack

What should a constant name start with in order to

comply with improved readability issues?

*A. an uppercase letter （增加可读性，常量使用大写的，而相同的问题还有：类使用）

How does an object without an explicit constructor

get created?

*A. The compiler inserts a constructor.

What is the lifetime of an object or method variable

in Java?

*B. duration of the defining code block