Using Scanner: the complement of Formatter : Scanner « File « Java Tutorial






  1. It reads formatted input and converts the input into the binary form.
  2. Scanner can read input from the console, a file, a string, or any source that implements the Readable interface or ReadableByteChannel.
  3. Scanner is packaged in java.util.

The following sequence creates a Scanner that reads the file test.txt:

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

public class MainClass {
  public static void main(String args[]) throws IOException {
    // Write output to a file.
    FileWriter fout = new FileWriter("test.txt");
    fout.write("2 3.4 5 6 7.4 9.1 10.5 done");
    fout.close();

    FileReader fin = new FileReader("Test.txt");

    Scanner src = new Scanner(fin);

    // Read and sum numbers.
    while (src.hasNext()) {
      if (src.hasNextDouble()) {
        System.out.println(src.nextDouble());
      }else{
        break;
      } 
    }
    fin.close();
  }
}
2.0
3.4
5.0
6.0
7.4
9.1
10.5








11.54.Scanner
11.54.1.Using Scanner to receive user input
11.54.2.Using Scanner: the complement of Formatter
11.54.3.In general, to use Scanner, follow this procedure
11.54.4.Creating a Scanner: read from standard input: Scanner conin = new Scanner(System.in)
11.54.5.Creating a Scanner to read from a string
11.54.6.Using Scanner to read several different unknown types of data
11.54.7.Setting Delimiters for Scanner
11.54.8.To obtain the current delimiter pattern: Pattern delimiter( )
11.54.9.Searching for the specified pattern within the next line of text
11.54.10.To find within the next count characters