In.java

/*************************************************************************
 * Compilation: javac In.java
 * Execution: java In (basic test --- see source for required files)
 *
 * Reads in data of various types from standard input, files, and URLs.
 *
 *************************************************************************/

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.HttpURLConnection;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.Locale;
import java.util.Scanner;
import java.util.regex.Pattern;

/**
 * <i>Input</i>. This class provides methods for reading strings
 * and numbers from standard input, file input, URLs, and sockets. 
 * <p>
 * The Locale used is: language = English, country = US. This is consistent
 * with the formatting conventions with Java floating-point literals,
 * command-line arguments (via {@link Double#parseDouble(String)})
 * and standard output. 
 * <p>
 * For additional documentation, see 
 * <a href="http://introcs.cs.princeton.edu/31datatype">Section 3.1</a> of
 * <i>Introduction to Programming in Java: An Interdisciplinary Approach</i> 
 * by Robert Sedgewick and Kevin Wayne.
 * <p>
 * Like {@link Scanner}, reading a token also consumes preceding Java
 * whitespace, reading a full line consumes
 * the following end-of-line delimeter, while reading a character consumes
 * nothing extra. 
 * <p>
 * Whitespace is defined in {@link Character#isWhitespace(char)}. Newlines
 * consist of \n, \r, \r\n, and Unicode hex code points 0x2028, 0x2029, 0x0085;
 * see <tt><a href="http://www.docjar.com/html/api/java/util/Scanner.java.html">
 * Scanner.java</a></tt> (NB: Java 6u23 and earlier uses only \r, \r, \r\n).
 *
 * @author David Pritchard
 * @author Robert Sedgewick
 * @author Kevin Wayne
 */
public final class In {
 
 private Scanner scanner;

 /*** begin: section (1 of 2) of code duplicated from In to StdIn */
 
 // assume Unicode UTF-8 encoding
 private static final String CHARSET_NAME = "UTF-8";

 // assume language = English, country = US for consistency with System.out.
 private static final Locale LOCALE = Locale.US;

 // the default token separator; we maintain the invariant that this value 
 // is held by the scanner's delimiter between calls
 private static final Pattern WHITESPACE_PATTERN
 = Pattern.compile("\\p{javaWhitespace}+");

 // makes whitespace characters significant 
 private static final Pattern EMPTY_PATTERN
 = Pattern.compile("");

 // used to read the entire input. source:
 // http://weblogs.java.net/blog/pat/archive/2004/10/stupid_scanner_1.html
 private static final Pattern EVERYTHING_PATTERN
 = Pattern.compile("\\A");

 /*** end: section (1 of 2) of code duplicated from In to StdIn */

 /**
 * Create an input stream from standard input.
 */
 public In() {
 scanner = new Scanner(new BufferedInputStream(System.in), CHARSET_NAME);
 scanner.useLocale(LOCALE);
 }

 /**
 * Create an input stream from a socket.
 */
 public In(java.net.Socket socket) {
 try {
 InputStream is = socket.getInputStream();
 scanner = new Scanner(new BufferedInputStream(is), CHARSET_NAME);
 scanner.useLocale(LOCALE);
 }
 catch (IOException ioe) {
 System.err.println("Could not open " + socket);
 }
 }

 /**
 * Create an input stream from a URL.
 */
 public In(URL url) {
 try {
 URLConnection site = url.openConnection();
 InputStream is = site.getInputStream();
 scanner = new Scanner(new BufferedInputStream(is), CHARSET_NAME);
 scanner.useLocale(LOCALE);
 }
 catch (IOException ioe) {
 System.err.println("Could not open " + url);
 }
 }

 /**
 * Create an input stream from a file.
 */
 public In(File file) {
 try {
 scanner = new Scanner(file, CHARSET_NAME);
 scanner.useLocale(LOCALE);
 }
 catch (IOException ioe) {
 System.err.println("Could not open " + file);
 }
 }


 /**
 * Create an input stream from a filename or web page name.
 */
 public In(String s) {
 try {
 // first try to read file from local file system
 File file = new File(s);
 if (file.exists()) {
 scanner = new Scanner(file, CHARSET_NAME);
 scanner.useLocale(LOCALE);
 return;
 }

 // next try for files included in jar
 URL url = getClass().getResource(s);

 // or URL from web
 if (url == null) { url = new URL(s); }

 URLConnection site = url.openConnection();

 // in order to set User-Agent, replace above line with these two
 // HttpURLConnection site = (HttpURLConnection) url.openConnection();
 // site.addRequestProperty("User-Agent", "Mozilla/4.76");

 InputStream is = site.getInputStream();
 scanner = new Scanner(new BufferedInputStream(is), CHARSET_NAME);
 scanner.useLocale(LOCALE);
 }
 catch (IOException ioe) {
 System.err.println("Could not open " + s);
 }
 }

 /**
 * Create an input stream from a given Scanner source; use with 
 * <tt>new Scanner(String)</tt> to read from a string.
 * <p>
 * Note that this does not create a defensive copy, so the
 * scanner will be mutated as you read on. 
 */
 public In(Scanner scanner) {
 this.scanner = scanner;
 }

 /**
 * Does the input stream exist?
 */
 public boolean exists() {
 return scanner != null;
 }
 
 /*** begin: section (2 of 2) of code duplicated from In to StdIn,
 * with all methods changed from "public" to "public static" ***/

 /**
 * Is the input empty (except possibly for whitespace)? Use this
 * to know whether the next call to {@link #readString()}, 
 * {@link #readDouble()}, etc will succeed.
 */
 public boolean isEmpty() {
 return !scanner.hasNext();
 }

 /**
 * Does the input have a next line? Use this to know whether the
 * next call to {@link #readLine()} will succeed. <p> Functionally
 * equivalent to {@link #hasNextChar()}.
 */
 public boolean hasNextLine() {
 return scanner.hasNextLine();
 }

 /**
 * Is the input empty (including whitespace)? Use this to know 
 * whether the next call to {@link #readChar()} will succeed. <p> Functionally
 * equivalent to {@link #hasNextLine()}.
 */
 public boolean hasNextChar() {
 scanner.useDelimiter(EMPTY_PATTERN);
 boolean result = scanner.hasNext();
 scanner.useDelimiter(WHITESPACE_PATTERN);
 return result;
 }


 /**
 * Read and return the next line.
 */
 public String readLine() {
 String line;
 try { line = scanner.nextLine(); }
 catch (Exception e) { line = null; }
 return line;
 }

 /**
 * Read and return the next character.
 */
 public char readChar() {
 scanner.useDelimiter(EMPTY_PATTERN);
 String ch = scanner.next();
 assert (ch.length() == 1) : "Internal (Std)In.readChar() error!"
 + " Please contact the authors.";
 scanner.useDelimiter(WHITESPACE_PATTERN);
 return ch.charAt(0);
 } 


 /**
 * Read and return the remainder of the input as a string.
 */
 public String readAll() {
 if (!scanner.hasNextLine())
 return "";

 String result = scanner.useDelimiter(EVERYTHING_PATTERN).next();
 // not that important to reset delimeter, since now scanner is empty
 scanner.useDelimiter(WHITESPACE_PATTERN); // but let's do it anyway
 return result;
 }


 /**
 * Read and return the next string.
 */
 public String readString() {
 return scanner.next();
 }

 /**
 * Read and return the next int.
 */
 public int readInt() {
 return scanner.nextInt();
 }

 /**
 * Read and return the next double.
 */
 public double readDouble() {
 return scanner.nextDouble();
 }

 /**
 * Read and return the next float.
 */
 public float readFloat() {
 return scanner.nextFloat();
 }

 /**
 * Read and return the next long.
 */
 public long readLong() {
 return scanner.nextLong();
 }

 /**
 * Read and return the next short.
 */
 public short readShort() {
 return scanner.nextShort();
 }

 /**
 * Read and return the next byte.
 */
 public byte readByte() {
 return scanner.nextByte();
 }

 /**
 * Read and return the next boolean, allowing case-insensitive
 * "true" or "1" for true, and "false" or "0" for false.
 */
 public boolean readBoolean() {
 String s = readString();
 if (s.equalsIgnoreCase("true")) return true;
 if (s.equalsIgnoreCase("false")) return false;
 if (s.equals("1")) return true;
 if (s.equals("0")) return false;
 throw new InputMismatchException();
 }

 /**
 * Read all strings until the end of input is reached, and return them.
 */
 public String[] readAllStrings() {
 // we could use readAll.trim().split(), but that's not consistent
 // since trim() uses characters 0x00..0x20 as whitespace
 String[] tokens = WHITESPACE_PATTERN.split(readAll());
 if (tokens.length == 0 || tokens[0].length() > 0)
 return tokens;
 String[] decapitokens = new String[tokens.length-1];
 for (int i = 0; i < tokens.length-1; i++)
 decapitokens[i] = tokens[i+1];
 return decapitokens;
 }

 /**
 * Reads all remaining lines from input stream and returns them as an array of strings.
 * @return all remaining lines on input stream, as an array of strings
 */
 public String[] readAllLines() {
 ArrayList<String> lines = new ArrayList<String>();
 while (hasNextLine()) {
 lines.add(readLine());
 }
 return lines.toArray(new String[0]);
 }


 /**
 * Read all ints until the end of input is reached, and return them.
 */
 public int[] readAllInts() {
 String[] fields = readAllStrings();
 int[] vals = new int[fields.length];
 for (int i = 0; i < fields.length; i++)
 vals[i] = Integer.parseInt(fields[i]);
 return vals;
 }

 /**
 * Read all doubles until the end of input is reached, and return them.
 */
 public double[] readAllDoubles() {
 String[] fields = readAllStrings();
 double[] vals = new double[fields.length];
 for (int i = 0; i < fields.length; i++)
 vals[i] = Double.parseDouble(fields[i]);
 return vals;
 }
 
 /*** end: section (2 of 2) of code duplicated from In to StdIn */
 
 /**
 * Close the input stream.
 */
 public void close() {
 scanner.close(); 
 }

 /**
 * Reads all ints from a file 
 * @deprecated Clearer to use 
 * <tt>new In(filename)</tt>.{@link #readAllInts()}
 */
 public static int[] readInts(String filename) {
 return new In(filename).readAllInts();
 }

 /**
 * Reads all doubles from a file
 * @deprecated Clearer to use 
 * <tt>new In(filename)</tt>.{@link #readAllDoubles()}
 */
 public static double[] readDoubles(String filename) {
 return new In(filename).readAllDoubles();
 }

 /**
 * Reads all strings from a file
 * @deprecated Clearer to use 
 * <tt>new In(filename)</tt>.{@link #readAllStrings()}
 */
 public static String[] readStrings(String filename) {
 return new In(filename).readAllStrings();
 }

 /**
 * Reads all ints from stdin 
 * @deprecated Clearer to use {@link StdIn#readAllInts()}
 */
 public static int[] readInts() {
 return new In().readAllInts();
 }

 /**
 * Reads all doubles from stdin
 * @deprecated Clearer to use {@link StdIn#readAllDoubles()}
 */
 public static double[] readDoubles() {
 return new In().readAllDoubles();
 }

 /**
 * Reads all strings from stdin
 * @deprecated Clearer to use {@link StdIn#readAllStrings()}
 */
 public static String[] readStrings() {
 return new In().readAllStrings();
 }
 
 /**
 * Test client.
 */
 public static void main(String[] args) {
 In in;
 String urlName = "http://introcs.cs.princeton.edu/stdlib/InTest.txt";

 // read from a URL
 System.out.println("readAll() from URL " + urlName);
 System.out.println("---------------------------------------------------------------------------");
 try {
 in = new In(urlName);
 System.out.println(in.readAll());
 }
 catch (Exception e) { System.out.println(e); }
 System.out.println();

 // read one line at a time from URL
 System.out.println("readLine() from URL " + urlName);
 System.out.println("---------------------------------------------------------------------------");
 try {
 in = new In(urlName);
 while (!in.isEmpty()) {
 String s = in.readLine();
 System.out.println(s);
 }
 }
 catch (Exception e) { System.out.println(e); }
 System.out.println();

 // read one string at a time from URL
 System.out.println("readString() from URL " + urlName);
 System.out.println("---------------------------------------------------------------------------");
 try {
 in = new In(urlName);
 while (!in.isEmpty()) {
 String s = in.readString();
 System.out.println(s);
 }
 }
 catch (Exception e) { System.out.println(e); }
 System.out.println();


 // read one line at a time from file in current directory
 System.out.println("readLine() from current directory");
 System.out.println("---------------------------------------------------------------------------");
 try {
 in = new In("./InTest.txt");
 while (!in.isEmpty()) {
 String s = in.readLine();
 System.out.println(s);
 }
 }
 catch (Exception e) { System.out.println(e); }
 System.out.println();


 // read one line at a time from file using relative path
 System.out.println("readLine() from relative path");
 System.out.println("---------------------------------------------------------------------------");
 try {
 in = new In("../stdlib/InTest.txt");
 while (!in.isEmpty()) {
 String s = in.readLine();
 System.out.println(s);
 }
 }
 catch (Exception e) { System.out.println(e); }
 System.out.println();

 // read one char at a time
 System.out.println("readChar() from file");
 System.out.println("---------------------------------------------------------------------------");
 try {
 in = new In("InTest.txt");
 while (!in.isEmpty()) {
 char c = in.readChar();
 System.out.print(c);
 }
 }
 catch (Exception e) { System.out.println(e); }
 System.out.println();
 System.out.println();

 // read one line at a time from absolute OS X / Linux path
 System.out.println("readLine() from absolute OS X / Linux path");
 System.out.println("---------------------------------------------------------------------------");
 in = new In("/n/fs/introcs/www/java/stdlib/InTest.txt");
 try {
 while (!in.isEmpty()) {
 String s = in.readLine();
 System.out.println(s);
 }
 }
 catch (Exception e) { System.out.println(e); }
 System.out.println();


 // read one line at a time from absolute Windows path
 System.out.println("readLine() from absolute Windows path");
 System.out.println("---------------------------------------------------------------------------");
 try {
 in = new In("G:\\www\\introcs\\stdlib\\InTest.txt");
 while (!in.isEmpty()) {
 String s = in.readLine();
 System.out.println(s);
 }
 System.out.println();
 }
 catch (Exception e) { System.out.println(e); }
 System.out.println();

 }

}