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Questions and Answers

Which package supports Java's basic input/output system?

java.io

What is a stream?

A sequence of data

Java uses the concept of streams to make input/output operations slower.

False

Which of the following classes are designed for byte streams?

InputStream Signup and view all the answers

The byte stream classes and character stream classes form the same hierarchies.

False Signup and view all the answers

What is the primary purpose of the File class in Java?

To manage files and directories Signup and view all the answers

Which method of the File class creates a new file?

createNewFile() Signup and view all the answers

Which method is used to create a folder or directory?

mkdir() Signup and view all the answers

The File class provides methods for reading and writing data to files.

False Signup and view all the answers

Which method of the File class returns the size of a file in bytes?

length() Signup and view all the answers

The `list()` method returns a single String object representing the directory's content.

False Signup and view all the answers

What is the primary function of byte streams in Java?

Handling input and output of bytes (8 bits) Signup and view all the answers

What is the primary function of character streams in Java?

Handling input and output of characters (16 bits) Signup and view all the answers

Character streams are always more efficient than byte streams.

False Signup and view all the answers

Match the following byte stream classes with their descriptions.

FileInputStream = Input stream that reads from a file. FileOutputStream = Output stream that writes to a file. BufferedInputStream = Used for buffered input streams. BufferedOutputStream = Used for buffered output streams. DataInputStream = Input stream that reads Java standard data types. DataOutputStream = Output stream that writes Java standard data types. PrintStream = Output stream with print() and println() methods. InputStream = Abstract class representing stream input. OutputStream = Abstract class representing stream output. Signup and view all the answers

Match the following character stream classes with their descriptions.

FileReader = Input stream that reads from a file. FileWriter = Output stream that writes to a file. BufferedReader = Handles buffered input streams. BufferedWriter = Handles buffered output streams. InputStreamReader = Input stream that translates bytes to characters. OutputStreamReader = Output stream that translates characters to bytes. PrintWriter = Output stream with print() and println() methods. Reader = Abstract class representing character stream input. Writer = Abstract class representing character stream output. Signup and view all the answers

What type of object is `System.in`?

InputStream Signup and view all the answers

What type of objects are `System.out` and `System.err`?

PrintStream Signup and view all the answers

While `System.out` and `System.err` are typically used for character-based I/O, they are fundamentally byte streams.

True Signup and view all the answers

Which of the following methods is NOT part of the PrintStream class?

read() Signup and view all the answers

What Java class is commonly used to read console input, automatically converting byte streams to character streams?

Scanner Signup and view all the answers

The `BufferedReader` class requires explicit conversion of byte streams to character streams.

False Signup and view all the answers

What method of the `BufferedReader` class reads data line by line?

readLine() Signup and view all the answers

The `BufferedWriter` class is primarily designed for input operations.

False Signup and view all the answers

Which of the following methods allows writing a newline character in a `BufferedWriter`?

newLine() Signup and view all the answers

What is the purpose of the `append()` method in the `BufferedWriter` class?

Append data to the output stream Signup and view all the answers

What Java class provides a preferred method for writing to the console in real-world programs, using a character-based approach?

PrintWriter Signup and view all the answers

Which of these constructors for the `PrintWriter` class is correct?

PrintWriter(OutputStream outputStream, boolean flushing) Signup and view all the answers

The `PrintWriter` class supports the `print()` and `println()` methods.

True Signup and view all the answers

The `write()` method of the `PrintStream` class can be used to write bytes to the console.

True Signup and view all the answers

What Java class handles the formatted output of data to the console?

PrintWriter Signup and view all the answers

What is the process of converting the state of an object into a byte stream called?

Serialization Signup and view all the answers

What is the process of converting a byte stream back into an object called?

Deserialization Signup and view all the answers

Serialization is typically used only for transferring objects across networks.

False Signup and view all the answers

What interface must a Java class implement to be eligible for serialization?

Serializable Signup and view all the answers

Which methods are used for serializing and deserializing objects using streams?

writeObject() and readObject() Signup and view all the answers

If a class is serializable, all of its subclasses are also serializable by default.

True Signup and view all the answers

What is the primary advantage of using packages in Java?

Organization and code reusability Signup and view all the answers

Packages in Java cannot be categorized as built-in or user-defined.

False Signup and view all the answers

What is the keyword used to create a package in Java?

package Signup and view all the answers

Which of these statements is the correct format for importing a specific class from a package?

import packagename.classname; Signup and view all the answers

The `import packagename.*;` statement imports all classes and interfaces from the specified package.

True Signup and view all the answers

What are the four access specifiers used in Java?

private, public, protected, and default Signup and view all the answers

Private members of a class are accessible from any part of the program.

False Signup and view all the answers

Public members of a class are accessible from any part of the program.

True Signup and view all the answers

Protected members of a class are accessible only within the same class.

False Signup and view all the answers

What is the default access specifier for class members?

Default Signup and view all the answers

The default access specifier allows access from all classes within the same package, even non-subclasses.

True Signup and view all the answers

Study Notes

Module III: Input/Output

Java's I/O system (input/output) is supported by the java.io package, encompassing file I/O.
Streams are used to facilitate I/O operations in Java, enabling faster processing. Streams represent a sequence of data.
Java uses streams to manage input and output operations.
The java.io package provides classes that support input and output operations.

The Stream Classes

Java's stream-based I/O is grounded in four abstract classes:
- InputStream: designed for byte streams.
- OutputStream: designed for byte streams.
- Reader: designed for character streams.
- Writer: designed for character streams.
Byte streams and character streams form separate hierarchies.
Character streams are used for working with characters or strings.
Byte streams are used for working with bytes or binary objects.

File and Directory Management

The java.io package supplies the File class for file and directory management.
File enables creating new files/folders, viewing properties, renaming, and deleting files/folders.
import java.io.* is necessary to use File class.
File class offers constructors for creating File objects from different inputs:
- File(String directoryPath)
- File(String directoryPath, String fileName)
- File(File dirObj, String fileName)
- File(URI uriObj)

Creating Files and Folders

createNewFile() creates an empty file.
mkdir() creates a directory.

Java FILE Class Methods

canRead(): checks if a file is readable.
canWrite(): checks if a file is writable.
createNewFile(): creates a file.
delete(): deletes a file.
exists(): checks if a file/directory exists.
getName(): returns the file's name.
getAbsolutePath(): returns the absolute path.
length(): returns file size in bytes.
list(): returns an array of files within a directory.
mkdir(): creates a directory.

Accessing File Properties (Methods)

toString(): returns a string representation of the File.
getName(): returns the file's or directory's name.
getPath(): returns the path of the file.
getAbsolutePath(): returns the absolute path.
getParent(): returns the parent directory's path.
exists(): checks if the file exists.
canWrite(): checks if the file can be written to.
canRead(): checks if the file can be read from.
isDirectory(): checks if the given path is a directory.
isFile(): checks if the given path is a file.
isAbsolute(): checks if the path is absolute.
isHidden(): checks if the file is hidden.

Renaming and Deleting Files

renameTo(File newFile) renames the file.
delete() deletes a file.
deleteOnExit() schedules a file's deletion.

Types of Streams

Byte Stream: Deals with input and output of bytes (8 bits). Used for binary data.
Character Stream: Handles input and output of characters (16 bits). Efficient for text data.

Byte Stream Classes

InputStream: Abstract base class for input byte streams.
OutputStream: Abstract base class for output byte streams.
FileInputStream: Reads from a file.
FileOutputStream: Writes to a file.
BufferedInputStream/BufferedOutputStream: Provide buffering for input/output.
DataInputStream/DataOutputStream: For reading/writing primitive data types.

Character Stream Classes

Reader: Abstract base class for character input.
Writer: Abstract base class for character output.
FileReader: Reads from a file.
FileWriter: Writes to a file.
BufferedReader/BufferedWriter: Provide buffering for character input/output.
PrintWriter: Designed for formatted printing.

File Input/Output Stream Methods

available(): Returns the estimated number of data bytes that are available in input stream.
read(): Reads one byte from an input stream.
read(byte[] b) reads bytes from stream to the array b.
read(byte[] b, int off, int len) reads len bytes from offset off to b.
skip(long n) skips over n bytes of input stream.
close(): Closes the stream.
write(byte[] b) writes bytes from b to an output stream.
write(byte[] b, int off, int len) writes from bytes in b starting from offset off for len bytes.
write(int b) writes a single byte b to the output stream.
close(): Closes the output stream.

Reading/Writing Data from/to Files using Different Streams

Methods for reading and writing data to files using various streams like FileInputStream, FileOutputStream, FileReader, FileWriter. Illustrates buffering techniques.

Reading Console Input

Scanner: Converts byte stream to character stream, enabling convenient input of various datatypes (int, byte, long, short, float, double, boolean).
BufferedReader: Used with InputStreamReader(System.in). Reads input from the command line.

Writing Console Output

Methods for writing output to the console (print, println, write).
PrintWriter is a recommended class for formatting output to the console.

Serialization

Serialization is the process of converting the state of an object into a byte stream.
writeObject() method ( ObjectOutputStream) serializes objects.
readObject() method ( ObjectInputStream) deserializes objects.
Serializable interface must be implemented for objects to be serializable.

Packages in Java

Packages group similar classes for organization.
Built-in packages provide core functionalities.
package statement defines packages.
import statement imports packages.

Access Protection

Packages define access levels (public, protected, default, private).
Access specifiers control code visibility and access.

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Questions and Answers

Which package supports Java's basic input/output system?

What is a stream?

Java uses the concept of streams to make input/output operations slower.

Which of the following classes are designed for byte streams?

The byte stream classes and character stream classes form the same hierarchies.

What is the primary purpose of the File class in Java?

Which method of the File class creates a new file?

Which method is used to create a folder or directory?

The File class provides methods for reading and writing data to files.

Which method of the File class returns the size of a file in bytes?

The list() method returns a single String object representing the directory's content.

What is the primary function of byte streams in Java?

What is the primary function of character streams in Java?

Character streams are always more efficient than byte streams.

Match the following byte stream classes with their descriptions.

Match the following character stream classes with their descriptions.

What type of object is System.in?

What type of objects are System.out and System.err?

While System.out and System.err are typically used for character-based I/O, they are fundamentally byte streams.

Which of the following methods is NOT part of the PrintStream class?

What Java class is commonly used to read console input, automatically converting byte streams to character streams?

The BufferedReader class requires explicit conversion of byte streams to character streams.

What method of the BufferedReader class reads data line by line?

The BufferedWriter class is primarily designed for input operations.

Which of the following methods allows writing a newline character in a BufferedWriter?

What is the purpose of the append() method in the BufferedWriter class?

What Java class provides a preferred method for writing to the console in real-world programs, using a character-based approach?

Which of these constructors for the PrintWriter class is correct?

The PrintWriter class supports the print() and println() methods.

The write() method of the PrintStream class can be used to write bytes to the console.

What Java class handles the formatted output of data to the console?

What is the process of converting the state of an object into a byte stream called?

What is the process of converting a byte stream back into an object called?

Serialization is typically used only for transferring objects across networks.

What interface must a Java class implement to be eligible for serialization?

Which methods are used for serializing and deserializing objects using streams?

If a class is serializable, all of its subclasses are also serializable by default.

What is the primary advantage of using packages in Java?

Packages in Java cannot be categorized as built-in or user-defined.

What is the keyword used to create a package in Java?

Which of these statements is the correct format for importing a specific class from a package?

The import packagename.*; statement imports all classes and interfaces from the specified package.

What are the four access specifiers used in Java?

Private members of a class are accessible from any part of the program.

Public members of a class are accessible from any part of the program.

Protected members of a class are accessible only within the same class.

What is the default access specifier for class members?

The default access specifier allows access from all classes within the same package, even non-subclasses.

Study Notes

Module III: Input/Output

The Stream Classes

File and Directory Management

Creating Files and Folders

Java FILE Class Methods

Accessing File Properties (Methods)

Renaming and Deleting Files

Types of Streams

Byte Stream Classes

Character Stream Classes

File Input/Output Stream Methods

Reading/Writing Data from/to Files using Different Streams

Reading Console Input

Writing Console Output

Serialization

Packages in Java

Access Protection

Studying That Suits You

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The `list()` method returns a single String object representing the directory's content.

What type of object is `System.in`?

What type of objects are `System.out` and `System.err`?

While `System.out` and `System.err` are typically used for character-based I/O, they are fundamentally byte streams.

The `BufferedReader` class requires explicit conversion of byte streams to character streams.

What method of the `BufferedReader` class reads data line by line?

The `BufferedWriter` class is primarily designed for input operations.

Which of the following methods allows writing a newline character in a `BufferedWriter`?

What is the purpose of the `append()` method in the `BufferedWriter` class?

Which of these constructors for the `PrintWriter` class is correct?

The `PrintWriter` class supports the `print()` and `println()` methods.

The `write()` method of the `PrintStream` class can be used to write bytes to the console.

The `import packagename.*;` statement imports all classes and interfaces from the specified package.