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  • 基本java类-In.java

    package com.algorithm.api;
    
    /*************************************************************************
     *  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 
    , 
    , 
    , 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 
    , 
    , 
    ).
     *
     *  @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();
    
        }
    
    }
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  • 原文地址:https://www.cnblogs.com/pacoson/p/4003578.html
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