Question 1

What interface must a class implement to indicate that objects of the class can be output and input as a stream of bytes?

Accepted Answer

The Serializable interface must be implemented to indicate that objects of the class can be output and input as a stream of bytes using serialization. Serialization is the process of converting an object into a stream of bytes, which can then be stored in a file or transmitted over a network. The Serializable interface is empty and serves only to identify the semantics of being serializable. It has no methods to be implemented.

Question 2

How do methods setIn,setOut and setErr affect the standard input,output and error streams?

Accepted Answer

The methods setIn, setOut, and setErr are used to redirect the standard input, output, and error streams respectively. This means that any data that would have been read from or written to these streams will now be read from or written to the streams that have been set using these methods. This redirection can be useful in situations where the default behavior of the standard input, output, or error streams needs to be modified.

Question 3

Which of the following classes is not used for file input?

Accepted Answer

Formatter is used for formatting and outputting data, not for file input. FileInputStream, FileReader, and ObjectInputStream are all used for reading data from files.

Question 4

Which of the following statements is false?

Accepted Answer

A relative path specifies a location starting from the current directory and does not need to start from the root directory. Absolute paths, not relative paths, start with the root directory.

Question 5

Which of the following statements is false?

Accepted Answer

All the statements provided are true. Statement A correctly describes the isAbsolute method for Path objects. Statement B accurately describes the getLastModifiedTime method of the Files class. Statement C correctly describes the size method of the Files class, including the platform-specific behavior for directories.

Question 6

Files static method ________ receives a Path and returns a boolean indicating whether that Path represents a directory on disk.

Accepted Answer

The correct method is "isDirectory". This method checks if the given path represents a directory on the disk and returns a boolean value accordingly. The other options are not valid methods and do not exist in the Files class.

Question 7

Path method ________ returns the String name of a file or directory without any location information.

Accepted Answer

The getFileName method returns the name of the file or directory without any location information.

Question 8

Which statement regarding Java files is false?

Accepted Answer

Java does not inherently support the concept of records stored in order by a record key within its file system operations. The handling of how data is structured, including any sorting or ordering, is up to the programmer to implement in their application code. Java files themselves are treated as streams of bytes, and any notion of records or their ordering is a higher-level abstraction not provided by the Java file I/O APIs directly.

Question 9

Records in a sequential file are not usually updated in place.Instead ________.

Accepted Answer

In a sequential file, data is written in a continuous stream, which means accessing a single record in the middle of the file can be time-consuming. Therefore, updating a record in a sequential file usually involves rewriting the entire file. The updated version of the record is written in its new location within the new file, and the old version of the record is deleted. This process is time-consuming but ensures that the data in the file is always up-to-date.

Question 10

Which of the following statements is true?

Accepted Answer

Class Scanner does not provide the ability to reposition to the beginning of the file. It only allows reading sequentially from the current position in the file.

Question 11

When all the contents of a file are truncated,this means that ________.

Accepted Answer

When a file is truncated, it means that all the data in the file is deleted or discarded. There is no backup file or exception thrown, it simply empties the contents of the file.

Question 12

Adding the services of one stream to another is known as ________.

Accepted Answer

The answer of Adding the services of one stream to...

Question 13

Which of the following classes enable input and output of entire objects to or from a file?
a)SerializedInputStream
b)SerializedOutputStream
c)ObjectInputStream
d)ObjectOutputStream
e)Scanner
f)Formatter

Accepted Answer

ObjectInputStream and ObjectOutputStream classes enable input and output of entire objects to or from a file through serialization. SerializedInputStream and SerializedOutputStream classes do not exist in Java. Scanner and Formatter classes allow input and output of formatted text, but not entire objects.

Question 14

Class ________ provides static methods for common file and directory manipulations,including methods for copying files;creating and deleting files and directories;getting information about files and directories;reading the contents of files;getting objects that allow you to manipulate the contents of files and directories;and more.

Accepted Answer

The correct answer is C) Files. The java.nio.file.Files class provides static methods for various file and directory operations, such as copying, creating, deleting, and reading files, as well as getting information about them.

Question 15

Streams that input bytes from and output bytes to files are known as ________.

Accepted Answer

Byte-based streams specifically deal with inputting and outputting bytes from files. The other options are not as specific and could include different types of streams that do not necessarily deal with files.

Question 16

Which of the following statements is false?

Accepted Answer

Data maintained in files is not often called transient data. Transient data refers to data that is only temporarily needed and is not meant to be stored long-term. Files are used for long-term retention of large amounts of data, so the statement in option D is false. Options A, B, and C are true statements.

Question 17

A(n)________ path starts from the directory in which the application began executing.

Accepted Answer

A relative path is a path that starts from the current directory or working directory. In this case, since the application began executing in a certain directory, a relative path would start from that directory. Absolute paths would start from the root directory. Parallel and comparative paths are not relevant in this context.

Question 18

What does the following statement do?
Scanner scanner = new Scanner(Paths.get("test.txt"));

Accepted Answer

The statement creates a Scanner object and uses the Paths class to retrieve the path of the "test.txt" file, which is then opened for input. Since the file is being read, it is assumed to be a text file rather than a binary file.

Question 19

Which of the following statements is false?

Accepted Answer

Path objects represent the location of a file or directory and provide file-processing capabilities, but they do not open files. Opening and processing files require other classes such as FileInputStream and BufferedReader.

Question 20

A serialized object is ________.

Accepted Answer

A serialized object is an object represented as a sequence of bytes used to store the object's data in a file. It can be later deserialized, which means it can be recreated in memory from the stored data in the file. Option B is incorrect because a deserialized object is created in memory, not a serialized object. Option C refers to an output stream used to write data to a file, but not specifically for serializing objects. Option D is incorrect because there is a correct answer among the choices.

Quiz 15: Files,streams and Object Serialization

What interface must a class implement to indicate that objects of the class can be output and input as a stream of bytes?

How do methods setIn,setOut and setErr affect the standard input,output and error streams?

Which of the following classes is not used for file input?

Which of the following statements is false?

Which of the following statements is false?

Files static method ________ receives a Path and returns a boolean indicating whether that Path represents a directory on disk.

Path method ________ returns the String name of a file or directory without any location information.

Which statement regarding Java files is false?

Records in a sequential file are not usually updated in place.Instead ________.

Which of the following statements is true?

When all the contents of a file are truncated,this means that ________.

Adding the services of one stream to another is known as ________.

Which of the following classes enable input and output of entire objects to or from a file? a) SerializedInputStream b) SerializedOutputStream c) ObjectInputStream d) ObjectOutputStream e) Scanner f) Formatter

Streams that input bytes from and output bytes to files are known as ________.

Which of the following statements is false?

A(n) ________ path starts from the directory in which the application began executing.

What does the following statement do? Scanner scanner = new Scanner(Paths.get("test.txt") ) ;

Which of the following statements is false?

A serialized object is ________.