算法Sedgewick第四版-第1章基础-005一封装输入(可以文件，jar包里的文件或网址)

package algorithms.util;

/******************************************************************************
*  Compilation:  javac In.java
*  Execution:    java In   (basic test --- see source for required files)
*  Dependencies: none
*
*  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.Socket;
// import java.net.HttpURLConnection;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.Locale;
import java.util.NoSuchElementException;
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 {

///// 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.

private Scanner scanner;

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

/**
* Initializes an input stream from a socket.
*
* @param  socket the socket
* @throws IllegalArgumentException if cannot open {@code socket}
* @throws NullPointerException if {@code socket} is {@code null}
*/
public In(Socket socket) {
if (socket == null) throw new NullPointerException("argument is null");
try {
InputStream is = socket.getInputStream();
scanner = new Scanner(new BufferedInputStream(is), CHARSET_NAME);
scanner.useLocale(LOCALE);
}
catch (IOException ioe) {
throw new IllegalArgumentException("Could not open " + socket);
}
}

/**
* Initializes an input stream from a URL.
*
* @param  url the URL
* @throws IllegalArgumentException if cannot open {@code url}
* @throws NullPointerException if {@code url} is {@code null}
*/
public In(URL url) {
if (url == null) throw new NullPointerException("argument is null");
try {
URLConnection site = url.openConnection();
InputStream is     = site.getInputStream();
scanner            = new Scanner(new BufferedInputStream(is), CHARSET_NAME);
scanner.useLocale(LOCALE);
}
catch (IOException ioe) {
throw new IllegalArgumentException("Could not open " + url);
}
}

/**
* Initializes an input stream from a file.
*
* @param  file the file
* @throws IllegalArgumentException if cannot open {@code file}
* @throws NullPointerException if {@code file} is {@code null}
*/
public In(File file) {
if (file == null) throw new NullPointerException("argument is null");
try {
scanner = new Scanner(file, CHARSET_NAME);
scanner.useLocale(LOCALE);
}
catch (IOException ioe) {
throw new IllegalArgumentException("Could not open " + file);
}
}

/**
* Initializes an input stream from a filename or web page name.
*
* @param  name the filename or web page name
* @throws IllegalArgumentException if cannot open {@code name} as
*         a file or URL
* @throws NullPointerException if {@code name} is {@code null}
*/
public In(String name) {
if (name == null) throw new NullPointerException("argument is null");
try {
// first try to read file from local file system
File file = new File(name);
if (file.exists()) {
scanner = new Scanner(file, CHARSET_NAME);
scanner.useLocale(LOCALE);
return;
}

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

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

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) {
throw new IllegalArgumentException("Could not open " + name);
}
}

/**
* Initializes an input stream from a given {@link 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.
*
* @param  scanner the scanner
* @throws NullPointerException if {@code scanner} is {@code null}
*/
public In(Scanner scanner) {
if (scanner == null) throw new NullPointerException("argument is null");
this.scanner = scanner;
}

/**
* Returns true if this input stream exists.
*
* @return <tt>true</tt> if this input stream exists; <tt>false</tt> otherwise
*/
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".

/**
* Returns true if input stream is empty (except possibly whitespace).
* Use this to know whether the next call to {@link #readString()},
* {@link #readDouble()}, etc will succeed.
*
* @return <tt>true</tt> if this input stream is empty (except possibly whitespace);
*         <tt>false</tt> otherwise
*/
public boolean isEmpty() {
return !scanner.hasNext();
}

/**
* Returns true if this input stream has a next line.
* Use this method to know whether the
* next call to {@link #readLine()} will succeed.
* This method is functionally equivalent to {@link #hasNextChar()}.
*
* @return <tt>true</tt> if this input stream is empty;
*         <tt>false</tt> otherwise
*/
public boolean hasNextLine() {
return scanner.hasNextLine();
}

/**
* Returns true if this input stream has more inputy (including whitespace).
* Use this method to know whether the next call to {@link #readChar()} will succeed.
* This method is functionally equivalent to {@link #hasNextLine()}.
*
* @return <tt>true</tt> if this input stream has more input (including whitespace);
*         <tt>false</tt> otherwise
*/
public boolean hasNextChar() {
scanner.useDelimiter(EMPTY_PATTERN);
boolean result = scanner.hasNext();
scanner.useDelimiter(WHITESPACE_PATTERN);
return result;
}

/**
* Reads and returns the next line in this input stream.
*
* @return the next line in this input stream; <tt>null</tt> if no such line
*/
public String readLine() {
String line;
try {
line = scanner.nextLine();
}
catch (NoSuchElementException e) {
line = null;
}
return line;
}

/**
* Reads and returns the next character in this input stream.
*
* @return the next character in this input stream
*/
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);
}

/**
* Reads and returns the remainder of this input stream, as a string.
*
* @return the remainder of this input stream, 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;
}

/**
* Reads the next token from this input stream and returns it as a <tt>String</tt>.
*
* @return the next <tt>String</tt> in this input stream
*/
public String readString() {
return scanner.next();
}

/**
* Reads the next token from this input stream, parses it as a <tt>int</tt>,
* and returns the <tt>int</tt>.
*
* @return the next <tt>int</tt> in this input stream
*/
public int readInt() {
return scanner.nextInt();
}

/**
* Reads the next token from this input stream, parses it as a <tt>double</tt>,
* and returns the <tt>double</tt>.
*
* @return the next <tt>double</tt> in this input stream
*/
public double readDouble() {
return scanner.nextDouble();
}

/**
* Reads the next token from this input stream, parses it as a <tt>float</tt>,
* and returns the <tt>float</tt>.
*
* @return the next <tt>float</tt> in this input stream
*/
public float readFloat() {
return scanner.nextFloat();
}

/**
* Reads the next token from this input stream, parses it as a <tt>long</tt>,
* and returns the <tt>long</tt>.
*
* @return the next <tt>long</tt> in this input stream
*/
public long readLong() {
return scanner.nextLong();
}

/**
* Reads the next token from this input stream, parses it as a <tt>short</tt>,
* and returns the <tt>short</tt>.
*
* @return the next <tt>short</tt> in this input stream
*/
public short readShort() {
return scanner.nextShort();
}

/**
* Reads the next token from this input stream, parses it as a <tt>byte</tt>,
* and returns the <tt>byte</tt>.
* <p>
* To read binary data, use {@link BinaryIn}.
*
* @return the next <tt>byte</tt> in this input stream
*/
public byte readByte() {
return scanner.nextByte();
}

/**
* Reads the next token from this input stream, parses it as a <tt>boolean</tt>
* (interpreting either <tt>"true"</tt> or <tt>"1"</tt> as <tt>true</tt>,
* and either <tt>"false"</tt> or <tt>"0"</tt> as <tt>false</tt>).
*
* @return the next <tt>boolean</tt> in this input stream
*/
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();
}

/**
* Reads all remaining tokens from this input stream and returns them as
* an array of strings.
*
* @return all remaining tokens in this input stream, as an array of strings
*/
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 this input stream and returns them as
* an array of strings.
*
* @return all remaining lines in this 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]);
}

/**
* Reads all remaining tokens from this input stream, parses them as integers,
* and returns them as an array of integers.
*
* @return all remaining lines in this input stream, as an array of integers
*/
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;
}

/**
* Reads all remaining tokens from this input stream, parses them as doubles,
* and returns them as an array of doubles.
*
* @return all remaining lines in this input stream, as an array of doubles
*/
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 */

/**
* Closes this input stream.
*/
public void close() {
scanner.close();
}

/**
* Reads all integers from a file and returns them as
* an array of integers.
*
* @param      filename the name of the file
* @return     the integers in the file
* @deprecated Replaced by <tt>new In(filename)</tt>.{@link #readAllInts()}.
*/
public static int[] readInts(String filename) {
return new In(filename).readAllInts();
}

/**
* Reads all doubles from a file and returns them as
* an array of doubles.
*
* @param      filename the name of the file
* @return     the doubles in the file
* @deprecated Replaced by <tt>new In(filename)</tt>.{@link #readAllDoubles()}.
*/
public static double[] readDoubles(String filename) {
return new In(filename).readAllDoubles();
}

/**
* Reads all strings from a file and returns them as
* an array of strings.
*
* @param      filename the name of the file
* @return     the strings in the file
* @deprecated Replaced by <tt>new In(filename)</tt>.{@link #readAllStrings()}.
*/
public static String[] readStrings(String filename) {
return new In(filename).readAllStrings();
}

/**
* Reads all integers from standard input and returns them
* an array of integers.
*
* @return     the integers on standard input
* @deprecated Replaced by {@link StdIn#readAllInts()}.
*/
public static int[] readInts() {
return new In().readAllInts();
}

/**
* Reads all doubles from standard input and returns them as
* an array of doubles.
*
* @return     the doubles on standard input
* @deprecated Replaced by {@link StdIn#readAllDoubles()}.
*/
public static double[] readDoubles() {
return new In().readAllDoubles();
}

/**
* Reads all strings from standard input and returns them as
*  an array of strings.
*
* @return     the strings on standard input
* @deprecated Replaced by {@link StdIn#readAllStrings()}.
*/
public static String[] readStrings() {
return new In().readAllStrings();
}

/**
* Unit tests the <tt>In</tt> data type.
*/
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();

}

}