Bifalgorithm post · Computer science one · File Input

How can a Scanner read input from a file?

How can a Scanner read input from a file? (Computer science one · File Input) — "Java provides several different classes and utilities that support manipulatin…

Ideas in this flowchart

  • Java provides classes and utilities for manipulating and processing files.
  • Most file operations may result in an IOException.
  • IOException is a checked exception that must be caught and handled.
  • Scanner is the easiest common way to read file input.
  • The File class represents a file resource but cannot open or close the actual file.
  • A Scanner can be initialized with a File object for a specified path.
  • The initialization uses a try-catch block with new Scanner(new File(...)).
  • FileNotFoundException must be caught and handled during Scanner initialization.
  • After creation, Scanner provides methods such as nextInt(), nextDouble(), next(), and nextLine().
  • hasNext() and nextLine() can read an entire file line by line for processing.
  • The Scanner should be closed after reading to free resources.
Feed/

How can a Scanner read input from a file?

No cover

Channel

Computer science one

1 page

"Java provides several different classes and utilities that support manipulating and processing files. In general, most file operations may result in an IOException, a checked exception that must be caught and handled. Though there are several ways that you can do file input, the easiest is to use the familiar Scanner class. We’ve previously used this class to read from the standard input, System.in, but it can also be used to read from a file using the File class in the java.io package. The File class is just a representation of a file resource and does not represent the actual file; it cannot be opened and closed. To initialize a Scanner to read from a file you can use the following:\n\nScanner s = null;\n\ntry {\n\ns = new Scanner(new File(\"/user/apps/data.txt\"));\n\n} catch (FileNotFoundException e) {\n\n//handle the exception here\n\n}\n\nWhen initializing a Scanner to read from a file, the exception FileNotFoundException must be caught and handled as it is a checked exception. Otherwise, once created, the Scanner class does not throw any checked exceptions. Once created, you can use the usual methods and functionality provided by the Scanner class, including reading the nextInt(), nextDouble(), next string using next(), or even the entire nextLine(). This last one can be used in conjunction with hasNext() to read an entire file, line-by-line:\n\nString line;\n\nwhile(s.hasNext()) {\n\nline = s.nextLine();\n\n//process the line\n\n}\n\nOnce we are done reading the file, we can close the Scanner to free up resources: s.close()."

Flowchart preview
👍
0
0 comments0 shares

Sign in to view and post comments.