Scanner vs. BufferedReader

Question

As far I know, the two most common methods of reading character-based data from a file in Java is using Scanner or BufferedReader. I also know that the BufferedReader read files efficiently by using a buffer to avoid physical disk operations. My questions are:

• Does Scanner performs as well as BufferedReader?
• Why would you choose Scanner over BufferedReader or vice versa?

Answer 1

There are different ways of taking input in java like:

1) BufferedReader 2) Scanner 3) Command Line Arguments

BufferedReader Read text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.

Where Scanner is a simple text scanner which can parse primitive types and strings using regular expressions.

if you are writing a simple log reader Buffered reader is adequate. if you are writing an XML parser Scanner is the more natural choice.

For more information please refer:

http://java.meritcampus.com/t/240/Bufferedreader?tc=mm69

Answer 2

Difference between BufferedReader and Scanner are following:

1. BufferedReader is synchronized but Scanner is not synchronized.
2. BufferedReader is thread safe but Scanner is not thread safe.
3. BufferedReader has larger buffer memory but Scanner has smaller buffer memory.
4. BufferedReader is faster but Scanner is slower in execution.

5. Code to read a line from console:

   BufferedReader:

    InputStreamReader isr=new InputStreamReader(System.in);
    BufferedReader br= new BufferedReader(isr);
    String st= br.readLine();
   

   Scanner:

   Scanner sc= new Scanner(System.in);
   String st= sc.nextLine();
   

Answer 3

The Main Differences:

1. Scanner

---

• A simple text scanner which can parse primitive types and strings using regular expressions.
• A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.

Example

 String input = "1 fish 2 fish red fish blue fish";
 Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");
 System.out.println(s.nextInt());
 System.out.println(s.nextInt());
 System.out.println(s.next());
 System.out.println(s.next());
 s.close(); 

prints the following output:

 1
 2
 red
 blue 

The same output can be generated with this code, which uses a regular expression to parse all four tokens at once:

 String input = "1 fish 2 fish red fish blue fish";

 Scanner s = new Scanner(input);
 s.findInLine("(\\d+) fish (\\d+) fish (\\w+) fish (\\w+)");
 MatchResult result = s.match();
 for (int i=1; i<=result.groupCount(); i++)
     System.out.println(result.group(i));
 s.close(); `

---

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2. BufferedReader:

   • Reads text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.

   • The buffer size may be specified, or the default size may be used. The default is large enough for most purposes.

In general, each read request made of a Reader causes a corresponding read request to be made of the underlying character or byte stream. It is therefore advisable to wrap a BufferedReader around any Reader whose read() operations may be costly, such as FileReaders and InputStreamReaders. For example,

BufferedReader in
   = new BufferedReader(new FileReader("foo.in"));

will buffer the input from the specified file. Without buffering, each invocation of read() or readLine() could cause bytes to be read from the file, converted into characters, and then returned, which can be very inefficient. Programs that use DataInputStreams for textual input can be localized by replacing each DataInputStream with an appropriate BufferedReader.

Source:Link

Answer 4

1. BufferedReader will probably give you better performance (because Scanner is based on InputStreamReader, look sources). ups, for reading from files it uses nio. When I tested nio performance against BufferedReader performance for big files nio shows a bit better performance.
2. For reading from file try Apache Commons IO.

Answer 5

In currently latest JDK6 release/build (b27), the Scanner has a smaller buffer (1024 chars) as opposed to the BufferedReader (8192 chars), but it's more than sufficient.

As to the choice, use the Scanner if you want to parse the file, use the BufferedReader if you want to read the file line by line. Also see the introductory text of their aforelinked API documentations.

• Parsing = interpreting the given input as tokens (parts). It's able to give back you specific parts directly as int, string, decimal, etc. See also all those nextXxx() methods in Scanner class.
• Reading = dumb streaming. It keeps giving back you all characters, which you in turn have to manually inspect if you'd like to match or compose something useful. But if you don't need to do that anyway, then reading is sufficient.

Answer 6

I prefer Scanner because it doesn't throw checked exceptions and therefore it's usage results in a more streamlined code.