Scja Java Se 6 Chapter 1

Front 1

What are packages?

Back 1

Packages are containers for classes. They define where .classes will be located in the hierarchical directory structure.

Front 2

What are the advantages of placing classes in a package?

Back 2

Decreases classes colliding, helps enable code reuse, maintainability, and the follows the guidelines of encapsulation and modulation.

Front 3

What is code collision?

Back 3

Having multiple files .java or .class with the same name in the same directory.

Hint 3

Example having two plane.java in the same directory.

Front 4

Advantage(s) of Package's Attribute of Class Coupling?

Back 4

Package dependencies are reduced

Front 5

Advantage(s) of Package's Attributes of System Coupling

Back 5

Package dependencies are reduced with system coupling

Front 6

Advantage(s) of a Package's attributes of package size?

Back 6

Typically, larger packages support reusability, smaller packages support maintainability.

Front 7

Advantage(s) of a Package's attributes regarding maintainability?

Back 7

Often, software changes can be limited to a single package when the package houses focused functionality

Front 8

Advantage(s) of a Package's attribute regarding naming?

Back 8

consider conventions when naming your packages. Use revers domain name for the package structure. Use lowercase characters delimited with underscores to separate words in package

Front 9

Where must the package statement be in the file?

Back 9

It must be the very first line of code at the top of the file.

Front 10

How many packages statements can be in a source file?

Back 10

At most 1 but it can have 0.

Front 11

What key word to you to include access to other classes in your source file?

Back 11

import

Front 12

What is the standard coding convention for package names?

Back 12

Reverse name of the domain name organization. Example. Organization scjaexam.com package name com.sjcaexam.utilities

Front 13

What do package names represent?

Back 13

It represents the file structure in which the .class files are found. Example com.scjaexam.utilities represents the directory: com/scjaexam.utilities/*.class

Front 14

Which words that begin a package are reserverd?

Back 14

java.* and javax.*

Front 15

Are package names normally upper or lowercase?

Back 15

lowercase

Front 16

What are some common packages from the Java SE 6 API will typically be on the exam?

Back 16

Java Abstract Window Toolkit (java.awt.*), Java Swing, Java Basic Input/Output (java.io.*), Java Networking, Java Utilities (java.util.*), Java Language (java.lang.*)

Front 17

Which package would you use to paint basic graphics and images?

Back 17

Abstract Window Toolkit (java.awt.*)

Front 18

Which package would you use to create lightweight components for GUI?

Back 18

Java Swing (javax.swing.*)

Front 19

Which package would you use to utilize data streams?

Back 19

Java Input/Output (java.io.*)

Front 20

Which package would you use to develop networking applications?

Back 20

Java Networking

Front 21

which package would you use to work with the collections framework, event model, and data/time facilities?

Back 21

Java Utilities (java.util.*)

Front 22

Which package would you use to utilize the core java classes and interfaces?

Back 22

Java Language (java.lang,*)

Front 23

What does this statement import, import java.net.*?

Back 23

Import all classes from the package java.net

Front 24

What does the import statement do, java.net.URL; ?

Back 24

Import only the URL class from the java.net package.

Front 25

What does this import statement do, import static java.awt.Color.*;?

Back 25

Imports all the static members of the Color class of the package java.awt.

Front 26

Is it better to explicitly import the classes you need or use the .* and why?

Back 26

It is better to explicitly state the classes because it allows other programmers to know which classes are being used throughout the class. Example import java.util.Vector is better than java.util.*.

Front 27

What are the 5 packages you need to know about for the SCJA exam?

Back 27

java.util, java.io, java.net, java.awt, java.lang

Front 28

What are the 4 main categories that are found in the java.util package?

Back 28

Java collection framework, date and time, internationalization, and miscellaneous

Front 29

What help does the Collections API help the Comparator interface?

Back 29

It helps sort collections where unnatural ordering occurs.

Front 30

What does the Comparable interface reside and what does it do?

Back 30

It resides in the java.lang package and helps in the sorting object by their natural ordering.

Front 31

What are 4 interfaces that you can find in java.util regarding Collections?

Back 31

List, Map, Set, Queue

Front 32

what are 3 classes that implement the List Interface and what is unique about these types of data structures?

Back 32

ArrayList, LinkedList, Vector. These data structures are based on positional access.

Front 33

What are 4 classes that implement the Map interface and what is unique about their data structure?

Back 33

HashMap, HashTable, LinkHashMap, TreeMap. These data structures map keys to values

Front 34

What are 3 classes that implement the Set interface and what is unique about their data structure?

Back 34

HashSet, LinkedHashset, and TreeSet. These data structures are based on element uniqueness.

Front 35

What is a class that implements the Queue interface and what is unique about its data structure?

Back 35

PriorityQueue. Queues are typically first in first out (FIFO). PriorityQueues order elements according to a supplied comprator.

Front 36

What Classes are used to represent Data and time capabilites in java.util

Back 36

Date, Calendar, and TimeZones

Front 37

What class in java.util is used to represent internationalization?

Back 37

Locale

Front 38

What are 4 other miscellaneous classes in java.util

Back 38

currency, Random, StringTokenizer(means for breaking down strings into tokens), Timer(provides a task scheduling facility).

Front 39

What is java.io used for?

Back 39

It is used for general system input and output regarding data streams, serialization, and the file system.

Front 40

What are the 2 major class hierarchies in java.io?

Back 40

Reader and writer.

Reader has the subclasses (BufferedReader, InputStreamReader, and FilterReader) that inherent the Reader class. FileReader inherents from the InputStremReader.


The Writer class has 3 subclasses (BufferedWriter, OutputStreamWriter, FilterWriter) that inherent from the Writer class. The FileWriter inherents from the OutputStreamWriter class

Front 41

What are 4 classes in the java.net package and what do they do?

Back 41

Socket (Provides for the implementation of client sockets), ServerSocket (Provides for the implementation of server sockets), URL (Represents a uniform resource locator), and Inet4Address(Represents an internet Protocol version 4 (IPv4) address).

Front 42

What is the java.awt used for?

Back 42

It is used to create HEAVYWEIGHT components in regards to creating user interfaces and painting associated graphics and images.

Front 43

What is preferred today for GUI applications java.awt or javax.swing?

Back 43

javax.swing

Front 44

What is one part of the java.awt that is still favored over javax.swing?

Back 44

AWT focus subsytem. It provides navigation control between components.

Front 45

What does javax.swing used for?

Back 45

It provides functionality for creating lightweight (pure-java) containers and components.

Front 46

How did they change the name of the javax.swing classes in order to distinguish it from the obsolete java.awt classes?

Back 46

They added a J to the beginning of the classes names. JLabel, JPanel...etc

Front 47

What design pattern does the javax.swing take advantage of and how?

Back 47

The MVC (model-view-controller). The model represents the state of each component. The view represents the components on the screen. The controller is the functionality that ties the UI components to the event.

Front 48

What does the x in javax stand for?

Back 48

It stands for packages comprised of Java standard extensions.

Front 49

Where do you find the java compiler tool in the JDK along with other tools?

Back 49

In the bin directory.

Front 50

What does the java compiler, javac, do?

Back 50

It converts your source code, .java files, into bytecode and stores the bytecode as .class files

Front 51

what is the general pattern for using the javac command?

Back 51

javac [options] [source files]. Example.

javac -d . com/*.java (means to compile all the java files in the com directory and then output the class files into a directory hierarchy describe by the package statement. Those creation of the top of the hierarchical structure directory should start at the current location.

Front 52

javac is actually what type of file?

Back 52

It is an executable file .exe on windows the javac.exe file extension is optional for the command and it doesn't exist on Unix-like systems

Front 53

what option do you use to explicity specify where you would like the compiled bytecode .class files to go?

Back 53

-d

example:

javac -d classes Hello.java would store the Hello.class file in the classes/ directory, which would look like this.
classes/Hello.java

Front 54

If the Hello.java had a package statement,
package com.sjcaexam.tutorial and the code was compiled using the javac -d classes Hello.java command, where would I find Hello.class bytecode?

Back 54

[present working directory]\classes\com\scjaexam\tutorial\Hello.class

Front 55

If you used the command:

javac -d classes Hello.java,

does the classes directory need to already exist for the command to execute?

Back 55

Yes!

Front 56

What option do you use in the javac command if you your source code had user-defined classes and packages and JVM might need to know where to find them?

Back 56

-classpath option or -cp (same thing)

Front 57

what does this command do?

javac -d classes -cp 3rdPartyCode\classes\;. Hello.java

Back 57

The compiler includes in its compilation any source files that are located 3rdPartyCode\classes as well as the current directory (.) It will output the bytecode to classes directory.

Front 58

what do you do to delimit different classpaths you need to use in the javac command.

Back 58

the semicolon ; separates different classpaths you need in windows

javac -cp com\practice; com\tutorial;.

On a POSIX system a colons

javac -cp com/practice:com/tutorial:.

Front 59

What is the path from source code to application?

Back 59

SourceCode.java -> (Compiler) javac -> SourceCode.class -> (Intrepter) java -> SourceCode application

Front 60

what does the java interpreter do?

Back 60

It takes bytecode .class files and turns it into machine code appropriated for the platform it is running on.

Front 61

What is the basic java interpreter command structure?

Back 61

java [-options] clas [args...]

example java -cp classes com.scjaexam.tutorial.Hello Bob

This means interpret the class file that is stored in the hierarchical structure com/scjaexam/tutorial/Hello.class. Look for this classpath hierachy in the classes directory, if you classes directory is located in the current directory.

The application Hello takes an argument. We are going to supply it with the String Bob for its argument.

Front 62

what does javaw do?

Back 62

It is an option you can use on Microsoft Windows to exclude the command window when running the program which is nice for GUI-based applications.

javaw.exe MainClass

Front 63

what does java MainClass & do?

Back 63

It runs the MainClass application in the background.

Front 64

What command do you use to interpret your Bytecode?

Back 64

-D option allows for setting of new property values. The usage is as follows:

java -D<name>=<value> class

Front 65

what option do you use to find out which java you are using and what are some valid and invalid placement of that option.

Back 65

answer -version
typical command, java -version.
will work:
java -version INVALID_ARGUMENT


java HelloWorld -version will start the appliaction HelloWorld but not the version