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
reads files efficiently by using a buffer to avoid physical disk operations.
My questions are:
Scanner
perform as well as BufferedReader
?Scanner
over BufferedReader
or vice versa?This question is related to
java
file-io
java.util.scanner
bufferedreader
Scanner
is used for parsing tokens from the contents of the stream while BufferedReader
just reads the stream and does not do any special parsing.
In fact you can pass a BufferedReader
to a scanner
as the source of characters to parse.
See this link, following is quoted from there:
A BufferedReader is a simple class meant to efficiently read from the underling stream. Generally, each read request made of a Reader like a FileReader causes a corresponding read request to be made to underlying stream. 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. Efficiency is improved appreciably if a Reader is warped in a BufferedReader.
BufferedReader is synchronized, so read operations on a BufferedReader can safely be done from multiple threads.
A scanner on the other hand has a lot more cheese built into it; it can do all that a BufferedReader can do and at the same level of efficiency as well. However, in addition a Scanner can parse the underlying stream for primitive types and strings using regular expressions. It can also tokenize the underlying stream with the delimiter of your choice. It can also do forward scanning of the underlying stream disregarding the delimiter!
A scanner however is not thread safe, it has to be externally synchronized.
The choice of using a BufferedReader or a Scanner depends on the code you are writing, if you are writing a simple log reader Buffered reader is adequate. However if you are writing an XML parser Scanner is the more natural choice.
Even while reading the input, if want to accept user input line by line and say just add it to a file, a BufferedReader is good enough. On the other hand if you want to accept user input as a command with multiple options, and then intend to perform different operations based on the command and options specified, a Scanner will suit better.
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:
Difference between BufferedReader and Scanner are following:
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();
The Main Differences:
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(); `
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
I suggest to use BufferedReader
for reading text. Scanner
hides IOException
while BufferedReader
throws it immediately.
I prefer Scanner
because it doesn't throw checked exceptions and therefore it's usage results in a more streamlined code.
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.
nextXxx()
methods in Scanner
class. Following are the differences between BufferedReader and Scanner
Thanks
BufferedReader
has significantly larger buffer memory than Scanner. Use BufferedReader
if you want to get long strings from a stream, and use Scanner
if you want to parse specific type of token from a stream.
Scanner
can use tokenize using custom delimiter and parse the stream into primitive types of data, while BufferedReader
can only read and store String.
BufferedReader
is synchronous while Scanner
is not. Use BufferedReader
if you're working with multiple threads.
Scanner
hides IOException while BufferedReader
throws it immediately.
The answer below is taken from Reading from Console: JAVA Scanner vs BufferedReader
When read an input from console, there are two options exists to achieve that. First using Scanner
, another using BufferedReader
. Both of them have different characteristics. It means differences how to use it.
Scanner treated given input as token. BufferedReader just read line by line given input as string. Scanner it self provide parsing capabilities just like nextInt(), nextFloat().
But, what is others differences between?
Scanner come with since JDK version 1.5 higher.
When should use Scanner, or Buffered Reader?
Look at the main differences between both of them, one using tokenized, others using stream line. When you need parsing capabilities, use Scanner instead. But, i am more comfortable with BufferedReader. When you need to read from a File, use BufferedReader, because it’s use buffer when read a file. Or you can use BufferedReader as input to Scanner.
Source: Stackoverflow.com