Java/File Input Output/Scanner

new Scanner(new BufferedReader(new FileReader("xanadu.txt")))

 
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 *
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 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
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 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
public class ScanXan {
  public static void main(String[] args) throws IOException {
    Scanner s = null;
    try {
      s = new Scanner(new BufferedReader(new FileReader("xanadu.txt")));
      while (s.hasNext()) {
        System.out.println(s.next());
      }
    } finally {
      if (s != null) {
        s.close();
      }
    }
  }
}

Perform the conversions after parsing the String

 
import java.io.File;
import java.util.Scanner;
public class Main {
  static void parseLine(String line) {
    Scanner lineScanner = new Scanner(line);
    lineScanner.useDelimiter("\\s*,\\s*");
    String name = lineScanner.next();
    int age = lineScanner.nextInt();
    boolean isCertified = lineScanner.nextBoolean();
    System.out.println("It is " + isCertified + " that " + name + ", age " + age
        + ", is certified.");
  }
  public static void main(String[] args) throws Exception {
    Scanner scanner = new Scanner(new File("fileName"));
    scanner.useDelimiter(System.getProperty("line.separator"));
    while (scanner.hasNext()) {
      parseLine(scanner.next());
    }
    scanner.close();
  }
}

Read file using Scanner class

 
 
import java.io.File;
import java.util.Scanner;
public class Main {
  public static void main(String[] args) throws Exception{
    File file = new File("data.txt");
    Scanner scanner = new Scanner(file);
    while (scanner.hasNextLine()) {
      String line = scanner.nextLine();
      System.out.println(line);
    }
  }
}

Read in the current contents of the java.net homepage

 
import java.net.URL;
import java.net.URLConnection;
import java.util.Scanner;
public class Main {
  public static void main(String[] args) throws Exception {
    URLConnection connection = new URL("http://java.net").openConnection();
    String text = new Scanner(connection.getInputStream()).useDelimiter("\\Z").next();
  }
}

Read user input from console using Scanner class

 
 
import java.util.Scanner;
public class Main {
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.print("Username: ");
    String username = scanner.nextLine();
    System.out.print("Password: ");
    String password = scanner.nextLine();
    System.out.print("What is 2 + 2: ");
    int result = scanner.nextInt();
    if (username.equals("admin") && password.equals("secret") && result == 4) {
      System.out.println("Welcome");
    } else {
      System.out.println("Invalid username or password!");
    }
  }
}

Scanning text with java.util.Scanner

 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
public class Main {
  private static void readFile(String fileName) throws Exception {
    File file = new File(fileName);
    FileReader reader = new FileReader(file);
    BufferedReader in = new BufferedReader(reader);
    String string;
    while ((string = in.readLine()) != null) {
      System.out.println(string);
    }
    in.close();
  }
  public static void main(String[] args) throws Exception {
    if (args.length != 1) {
      System.err.println("usage: java TextReader " + "file location");
      System.exit(0);
    }
    readFile(args[0]);
  }
}

Simplify the code in TextReader by using java.util.Scanner

 
import java.io.File;
import java.util.Scanner;
public class Main {
  static void readFile(String fileName) throws Exception {
    File file = new File(fileName);
    Scanner scanner = new Scanner(file);
    while (scanner.hasNext()) {
      System.out.println(scanner.next());
    }
    scanner.close();
  }
  public static void main(String[] args) throws Exception{
    if (args.length != 1) {
      System.err.println("usage: java TextScanner1" + "file location");
      System.exit(0);
    }
    readFile(args[0]);
  }
}

Split a string using Scanner class

 
 
import java.io.File;
import java.util.Scanner;
public class Main {
  public static void main(String[] args) throws Exception {
    File file = new File("data.txt");
    Scanner scanner = new Scanner(file);
    while (scanner.hasNextLine()) {
      String line = scanner.nextLine();
      Scanner lineScanner = new Scanner(line);
      lineScanner.useDelimiter(",");
      while (lineScanner.hasNext()) {
        String part = lineScanner.next();
        System.out.print(part + ", ");
      }
      System.out.println();
    }
  }
}