Four ways to read a file in java. I have tested an execution time of them using 1,37 MB text file with 108825 lines. Result of tests is in a first comment of each method and is specified in milliseconds.
1 Read entire file at once
1.1 FileInputStream with read()
// execution time: 7 - 8 ms
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
File file = new File("C:\\test.txt");
InputStream is = new FileInputStream(file);
byte[] temp = new byte[1024];
int read;
while ((read = is.read(temp)) >= 0) {
buffer.write(temp, 0, read);
}
byte[] data = buffer.toByteArray();
System.out.println(new String(data));
PS: remember that
read(byte[] b) doesn't do what you think it does ->
link
1.2 FileInputStream with readFully()
// execution time: 11 - 12 ms
File file = new File("C:\\test.txt");
DataInput input = new DataInputStream(new FileInputStream(file));
byte[] bufferArray = new byte[(int) file.length()];
input.readFully(bufferArray);
String value = new String(bufferArray);
2 Read file line by line
2.1 BufferedReader with readLine()
// execution time: 19 - 20 ms
FileInputStream fStream = new FileInputStream("C:\\test.txt");
DataInputStream in = new DataInputStream(fStream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String line;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
2.2 Scanner with nextLine(
// execution time: 196 - 216 ms
File file = new File("c://test.txt");
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
scanner.nextLine();
System.out.println(line);
}
scanner.close();
