CODEWITHSUNDEEP
javafile-io
Aritra Roy
Aritra Roy

Reputation: 15615

Does FileReader and FileWriter uses an internal buffer?

I know that the FileReader and FileWriter reads and writes characters one-by-one. So, it should me making a system call everytime.

But my question is that, does it internally use a buffer to optimize IO performance?

Otherwise, reading an array of characters like here,

public int read(char[] cbuf, int offset, int length)

would require a system call for each of the characters being read.

Or writing a portion of String like here,

public void write(String str, int off,int len)

would be quite heavy isn't it?

Upvotes: 1

Views: 108

Answers (3)

Joni
Joni

Reputation: 111219

FileReader and FileWriter derive from InputStreamReader and OutputStreamWriter. The implementations of these do use buffers internally to make conversions between bytes and characters more efficient, for example OpenJDK uses 8kB buffers (see the StreamDecoder and StreamEncoder classes). The API specification gives you no guarantees though and recommends that you use BufferedReader and BufferedWriter for IO performance.

Upvotes: 4

Rahman
Rahman

Reputation: 3785

No Aritra. It doesnt use internal buffer. That job is done by BufferedReader. BufferedReader internally buffers the reading of characters. It reads text from a character input stream/file system, and stores it into a buffer. So when a user make a request for next character it will return that character from the buffer , not from the file system. You can wrap BufferedReader around FileReader :

FileReader fr = new FileReader("test.txt");
BufferedReader reader = new BufferedReader(fr);

Upvotes: 0

user207421
user207421

Reputation: 310850

No, but they respectively use InputStreamReader and OutputStreamWriter, which both have buffers.

Upvotes: 1

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