data课程程序代写、代写Java编程

日期：2022-02-19 11:41

• any missing or incomplete elements of the code

• any changes made to the original API

• the amount of time spent for this assignment

• suggestions or comments if any

No submission of the above document will lead to a loss of 5 grade points. Also, please add

comments in your code.

In this programming assignment, you need to implement several classes for representing both

relational and non-relational data. You first need to install and run Eclipse on your machine and

import the “hdb data” project (see Appendix A). Please generate an API document (see Appendix

B) and then take a look at that document as well as the source code to familiarize yourself with

this assignment. This assignment provides you with a set of incomplete classes. To see these

classes, choose the “src” source folder and then either the “hdb.data.relational” package or

the “hdb.data.nonrelational” package. You will need to write code for these classes. Your code

will be graded by running a set of unit tests (see the unit tests in the “test” source folder which

use JUnit1

) and then examining your code. For details of running these tests, refer to Appendix

A. Note that passing unit tests does not necessarily guarantee that your implementation is correct

and efficient. Please make sure that your code would not cause problems even in situations not

covered by the unit tests. If you have questions, please contact the TA(s) or the instructor. The

remainder of this document describes the components that you need to implement.

Part 1. Relation Schema (40 points)

A RelationSchema represents the schema of a relation. A RelationSchema contains an array

attributeNames which stores the names of attributes (e.g., { "ID", "Name" }) and another

array attributeTypes which contains the types of the attributes (e.g., { Integer.class,

String.class }). In this part, you need to complete the following methods of the RelationSchema

class:

• size(): returns the number of attributes in the RelationSchema.

• attributeName(int attributeIndex): returns the name of the attribute specified by attributeIndex.

If attributeIndex is set to an invalid value (e.g., -1), then attributeName(int attributeIndex)

needs to return an InvalidAttributeIndexException. For example, if array attributeNames

is set to { "ID", "Name" }, then attributeName(0) and attributeName(1) must return

"ID" and "Name", respectively. On the other hand, attributeName(2) must throw an

InvalidAttributeIndexException.

1

http://junit.org

1

• attributeType(int attributeIndex): returns the type of the attribute specified by attributeIndex.

If attributeIndex is set to an invalid value (e.g., -1), then attributeName(int attributeIndex)

needs to return an InvalidAttributeIndexException. For example, if array attributeTypes

is set to { Integer.class, String.class }, then attributeType(0) and attributeType(1)

must return Integer.class and String.class, respectively. Also, attributeType(2) must

throw an InvalidAttributeIndexException.

• attributeIndex(String attributeName): returns the index of the attribute specified by

attributeName. For example, if array attributeNames is set to { "ID", "Name" }, then

attributeIndex("ID"), attributeIndex("Name"), and attributeIndex("Address") must

return 0, 1, and null, respectively.

• save(String fileName): writes the RelationSchema (on which this method is called) to

the file specified by fileName. This method needs to create a FileOutputStream using

fileName and then an ObjectOutputStream that writes to that FileOutputStream. The

RelationSchema on which this method is called needs to be written to the ObjectOutputStream

using ObjectOutputStream#writeObject(Object). If your code throws a

java.io.NotSerializableException, address that problem after understanding the basics

of Java object serialization. You would need to make a change outside the save(String

fileName) method. Details of serialization can be found at:

https://docs.oracle.com/javase/8/docs/technotes/guides/serialization/.

Please make sure that your code passes all of the 5 unit tests in RelationSchemaTest. These

unit tests verify the 5 methods mentioned above using one instance of RelationSchema containing

2 attributes ("ID" and "Temperature" of the Integer and Double types, respectively) and another

instance containing 3 attributes ("ID", "Name", and "Address" of the Integer, String, and String

types, respectively) .

Part 2. Tuple (40 points)

A Tuple is a record (i.e., a row) in a relation. Each Tuple contains the values of certain

attributes that collectively represent an entity. For example, a tuple { 123, "John" } in a relation

with attributes "ID" and "Name" would represent a person whose ID is 123 and name is "John".

Each Tuple has an array attributeValues which stores the values of attributes defined in the

corresponding RelationSchema.

In this part, you need to implement the following methods in Tuple.java:

• setAttribute(int attributeIndex, Object o): sets the value of the attribute specified by

attributeIndex to Object o. For example, setAttribute(0, 123) and setAttribute(1,

"John") would set attributeValues[0] to 123, and attributeValues[1] to "John", respectively.

If the specified attribute value (o) is not compatible with the type of the attribute,

then the method needs to throw a TypeException. In other words, when the RelationSchema

has an array of types { Integer.class, String.class }, setAttribute(0, "John") must

throw a TypeException since the attribute at index 0 is of the Integer type and thus cannot

be set to "John". Consider using Class#isInstance(Object) to check type compatibility.

Also, if attributeIndex is set to an invalid value (e.g., -1), then setAttribute(int

attributeIndex, Object o) needs to return an InvalidAttributeIndexException.

• writeAttributes(ObjectOutputStream out): writes the attribute values of the Tuple to

the specified ObjectOutputStream. This method needs to call Tuple#write(Object o,

ObjectOutputStream out) to write each attribute value to the ObjectOutputStream. As

explained below, Java object serialization tends to incur high space overhead. The purpose

of writeAttributes(ObjectOutputStream out) is to reduce this overhead through

2

custom serialization (instead of the standard Java object serialization). Right after implementing

this method, consider verifying your implementation using the writeAttributes

test in TupleTest as explained below this list of methods to implement.

• write(Object o, ObjectOutputStream out): writes the specified Object to the specified

ObjectOutputStream. Writing Object o to the ObjectOutputStream using

ObjectOutputStream#writeObject(Object) (which performs the standard Java object serialization)

may incur high space overhead. Therefore, write(Object o, ObjectOutputStream

out) needs to call (i) ObjectOutputStream#writeInt(int) if the given Object is of the

Integer type, (ii) ObjectOutputStream#writeDouble(double) if the given Object is of the

Double type, and (iii) ObjectOutputStream#writeObject(Object) only in the other cases.

• read(Class<?> type, ObjectInputStream in): reads an object from the specified

ObjectInputStream. This method needs to call (i) ObjectInputStream#readInt() if the

specified type is Integer.class, (ii) ObjectInputStream#readDouble() if the specified

type is Double.class, and (iii) ObjectInputStream#readObject() otherwise.

Please verify your code using the tests in TupleTest. Your code can pass the writeAttributes

test in TupleTest as long as writeAttributes(ObjectOutputStream out) is correctly implemented

(even if write(Object o, ObjectOutputStream out) and

read(Class<?> type, ObjectInputStream in) are not completed). The following result from

the writeAttributes test shows the difference between the standard Java object serialization and

our custom serialization (even when it is partially implemented) given a Tuple contaning just one

4-byte int value and one 8-byte double value.

size of tuple [ 1 , 5 . 0 ] ( standard Java serialization ) : 538

size of tuple [ 1 , 5 . 0 ] ( custom serialization ) : 134

The writeRead test in TupleTest requires complete implementation of

write(Object o, ObjectOutputStream out) and read(Class<?> type, ObjectInputStream in).

When Part 2 is completed, the writeRead test will produce the following result:

size of tuple [ 1 , 5 . 0 ] ( standard Java serialization ) : 538

size of tuple [ 1 , 5 . 0 ] ( custom serialization ) : 18

The above result shows 6 bytes of additional data written in addition to the 4-byte int and 8-byte

double values due to some inherent overhead caused by the use of ObjectOutputStream. This

additional space overhead is still much lower than that of the standard Java object serialization.

In other words, the change in space usage from 538 bytes to 18 bytes shows the benefit of custom

serialization over the standard Java object serialization.

Part 3. Non-Relational Data (10 points)

In this part, you need to complete the CollectionSchema and DataObject classes in the

hdb.data.nonrelational package. These two classes are similar to RelationSchema and Tuple,

but their main difference is that they support non-relational data. In detail, while all Tuples in

the same relation must have the same set of attributes, DataObjects in the same collection can

have different attributes. For example, a DataObject can have three attributes "ID", "Name", and

"Height" and another DataObject in the same collection can have "ID" and "Weight".

A CollectionSchema uses the following two HashMaps to maintain a number of attributes:

• name2index: maps attribute names to attribute indices. For example, when "ID" and "Name"

are assigned indices 0 and 1, name2index will look like {"ID"=0, "Name"=1}.

• index2name: maps attribute indices to attribute names. For example, when "ID" and "Name"

are assigned indices 0 and 1, index2name will look like {0="ID", 1="Name"}.

3

In CollectionSchema, you need to complete the following methods:

• int[] attributeIndex(String attributeName): returns the index (as an int array) of the

attribute specified by attributeName. For example, suppose that "ID" and "Name" are assigned

indices 0 and 1, respectively. Then, attributeIndex("ID") and attributeIndex("Name")

need to return arrays {0} and {1}, respecitvely. The reason for returning an int array

instead of a single int will be discussed in detail in Part 4. If the attribute specified

by attributeName is not yet regisered in name2index, then this attributeIndex(String

attributeName) method needs to register that attribute (essentially, the name and index

of that attribute) in name2index. In this case, it also needs to update index2name accordingly.

For examle, suppose that "ID" and "Name" are assigned indices 0 and 1, respectively.

If attributeIndex("Height") is called in this case, ("Height", 2) needs to be added to

name2index and (2, "Height") needs to be added to index2name.

• attributeName(int[] attributeIndex): returns the name of the attribute specified by

attributeIndex. In the example mentioned above, attributeName({0}) and attributeName({1})

need to return "ID" and "Name", respecitvely. Again, the reason for using an int array instead

of a single int for attributeIndex will be discussed in detail in Part 4.

In DataObject.java, you need to implement the following methods:

• setAttribute(String attributeName, Object o): sets the attribute specified by attributeName

to o.

• attributeValue(int[] attributeIndex): returns the value of the attribute specified by

attributeIndex.

• writeAttributes(ObjectOutputStream out): writes the attributes of the DataObject on

which the method is called to the specified ObjectOutputStream.

• DataObject(CollectionSchema schema, ObjectInputStream in): constructs a DataObject

from the specified ObjectInputStream. This constructor needs to throw an

InvalidAttributeIndexException if an attribute index stored in the ObjectInputStream

is not registered in the CollectionSchema for this DataObject (i.e., an invalid attribute

index).

When you complete the above methods, make sure that your implementation passes the two

unit tests named CollectionSchemaTestBasic and DataObjectTestBasic.

Part 4. Non-Relational Data - Hierarchical Data Representation (5 points)

As mentioned in Part 3, DataObjects in the same collection can have different attributes.

Furthermore, a DataObject may have a hierarchical structure. For example, for a DataObject, the

value of the "Name" attribute can be another DataObject having "FirstName" and "LastName" as

its attributes. In this case, given the former DataObject, "Name.FirstName" and "Name.LastName"

would represent the first name and second name of a person, respectively.

In addition to name2index and index2name, a CollectionSchema uses a HashMap named

index2schema to maintain a hierarchy of attributes. index2schema maps an attribute index to

a CollectionSchema if the corresponding attribute consists of sub-attributes. For example, if

"ID" has no sub-attributes and "Name" has two sub-attributes FirstName and SecondName, then

index2schema will look like {1={0="FirstName", 1="LastName"}}. In this example, {0="FirstName",

1="LastName"}) represents a CollectionSchema consisting of attributes "FirstName" and "LastName".

Also note that index2schema in the above example does not have any entry for "ID" because it

does not have any sub-attributes.

4

In CollectionSchema, you need to extend the following methods to support hierarchical data

representations:

• int[] attributeIndex(String attributeName): returns the index (as an int array) of

the attribute specified by attributeName. For example, suppose that (i) "ID" and "Name"

are assigned indices 0 and 1, respectively, and (ii) "Name" has sub-attributes "FirstName"

and "LasstName" which are assigned 0 and 1, respectively. Then, attributeIndex("ID")

and attributeIndex("Name") need to return arrays {0} and {1}, respecitvely. Furthermore,

attributeIndex("Name.FirstName") and attributeIndex("Name.LastName") need

to return arrays {1, 0} and {1, 1}, respecitvely.

• attributeName(int[] attributeIndex): returns the name of the attribute specified by

attributeIndex. In the example mentioned above, attributeName({0}) and attributeName({1})

need to return "ID" and "Name", respecitvely. Furthermore, attributeName({1, 0}) and

attributeName({1, 1}) need to return "Name.FirstName" and "Name.LastName", respecitvely.

You also need to extend DataObject.java to enable hierarchical data representations.

When you complete the above methods, run the two unit tests named CollectionSchemaTestAdvanced

and DataObjectTestAdvanced. These tests check whether or not CollectionSchema and DataObject

can represent data in a hierarchical manner.

Appendix A. Installing Eclipse and Importing a Java Project

1. Visit:

http://www.eclipse.org/downloads/

2. From the web site, download the eclipse installer (those for Linux, Windows, and Mac OS X

are available) and then choose “Eclipse IDE” and install it.

3. After finishing installation, start Eclipse.

4. When Eclipse runs for the first time, it asks the user to choose the workspace location. You

may use the default location.

5. In the menu bar, choose “File” and then “Import”. Next, select “General” and “Existing

Projects into Workspace”. Then, click the “Browse” button and select the “hdb data.zip”

file contained in this assignment package.

6. Once the project is imported, you can choose the “hdb.data” package in the “test” source

folder. Then, you can run one among RelationSchemaTest.java, TupleTest.java,

CollectionSchemaTestBasic.java, CollectionSchemaTestAdvanced.java,

DataObjectTestBasic.java, and DataObjectTestAdvanced.java by clicking the icon highlighted

in Figure 1.

Appendix B. Creating API documents using javadoc

One nice feature of Java is its support for “documentation comments”, or “javadoc” comments,

which you can use to automatically produce documentation for your code. Javadoc comments start

with “/**”. Inside a javadoc comment, there are some special symbols, like @param and @return.

You can create HTML-based API documents from the source as follows:

1. Click the “hdb data” project icon in the Navigator or Project Explorer window.

5

Figure 1: Eclipse

2. Select “Generate Javadoc” from the “Project” menu.

3. In the “Generate Javadoc” dialog box, press the “Finish” button.

As it runs, it tells you that it is generating various things. When it is finished, a few new folders

should appear in your project: doc, doc.resources, and so on. See what got generated (to open

the newly created HTML documentation files in a web browser window, just double-click them;

you can start with “index.html”).

6