Question

Determine which of the following statements are true and which are false. If \(f a l\) se, explain why. a) The programmer must explicitly create the stream objects System. in, System. out and System .err. b) When reading data from a file using class Scanner, if the programmer wishes to read data in the file multiple times, the file must be closed and reopened to read from the beginning of the file. This moves the file-position pointer back to the beginning of the file. c) Method exists of class File returns true if the name specified as the argument to the File constructor is a file or directory in the specified path. d) Binary files are human readable. e) An absolute path contains all the directories, starting with the root directory, that lead to a specific file or directory. f) Class Formatter contains method printf, which enables formatted data to be output to the screen or to a file.

Short answer

a) False, b) True, c) True, d) False, e) True, f) True.

Step-by-step solution

Evaluate Statement a

The statement suggests that the programmer has to explicitly create the `System.in`, `System.out`, and `System.err` stream objects. In Java, these stream objects are provided by default and are automatically available for input and output operations. Therefore, the statement is false. There is no need for the programmer to explicitly create these stream objects.

Evaluate Statement b

The statement claims that, when using `Scanner` to read from a file, the file must be closed and reopened to move the file-position pointer back to the beginning. This is true. When using `Scanner`, you cannot rewind to the beginning of a file directly, so closing and reopening the file is necessary to reset the position.

Evaluate Statement c

This statement explains that the `exists` method of the `File` class returns true if the file or directory exists in the specified path. This is indeed true, as `exists()` checks for the presence of both files and directories in the given path.

Evaluate Statement d

Binary files are typically not human readable as they are composed of binary data (0s and 1s) that are interpreted by computers, not directly readable by humans like text files. Thus, the statement that binary files are human readable is false.

Evaluate Statement e

An absolute path contains all directories starting from the root directory to the specific file or directory. This means it includes the complete path hierarchy. Therefore, this statement is true.

Evaluate Statement f

The statement indicates that the `Formatter` class contains a `printf` method for formatted output. In fact, `Formatter` in Java does provide formatting functions and `printf` for output to a file, so the statement is true.

Key concepts

Java Streams

In Java, streams provide a way to handle input and output operations efficiently. Java provides built-in stream objects such as `System.in`, `System.out`, and `System.err`. These are automatically available for use and do not require explicit creation by the programmer.
Java streams allow seamless reading and writing of data.

• System.in: A predefined input stream, typically connected to keyboard input.
• System.out: A predefined output stream, commonly used to print data to the console.
• System.err: Similar to System.out but used for error messages.

Using streams, you can perform input and output operations at byte levels for various types of data.

Java Scanner

The `Scanner` class in Java is utilized for parsing primitive types and strings using regular expressions. It's a popular class for reading input, especially from files or keyboard input.
When using `Scanner` to read from files, there's a catch: you cannot go back to a previous position. If you want to reread the same file, you'll need to close and reopen it. This resets the file-position pointer to the start of the file. This characteristic is important to note for effective file handling in Java.
With `Scanner`, you can tokenize input into usable formats like:

• int nextInt() - Reads the next integer.
• double nextDouble() - Reads the next double value.
• String nextLine() - Reads the entire line as a string.

Java Formatter

Java's `Formatter` class is a utility for formatting data. It can output both to the console and files. The class supports format specifiers similar to `printf` in C for formatted output.
The `printf` method is part of the `Formatter` class, and it offers detailed control over data representation, making it highly versatile for any formatted I/O operations.
Using `Formatter` in Java includes capabilities like:

• %d - Decimal integer.
• %f - Floating-point number.
• %s - String.

You can dynamically format strings, integers, and floats to professional-looking outputs, enhancing readability and presentation.

Absolute and Relative Paths

Understanding paths in file management is key to manipulating files and directories. Java supports both absolute and relative paths.
An absolute path provides the complete direction from the root directory to the desired file or folder, ensuring the precise location is always reachable.
On the other hand, a relative path is defined concerning the current working directory. This path type is shorter but requires knowledge of the current folder structure.
Java's `File` class helps manage these paths, allowing operations like existence checks and path retrieval:

• An absolute path example: /Users/JohnDoe/Documents/report.txt
• A relative path example: Documents/report.txt

Choosing between these paths depends on the application's needs for location flexibility or specificity.