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Npuzzle/src/algs4/util/StdIn.java

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/******************************************************************************
* Compilation: javac StdIn.java
* Execution: java StdIn (interactive test of basic functionality)
* Dependencies: none
*
* Reads in data of various types from standard input.
*
******************************************************************************/
package algs4.util;
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;
/**
* The {@code StdIn} class provides static methods for reading strings
* and numbers from standard input.
* These functions fall into one of four categories:
* <ul>
* <li>those for reading individual tokens from standard input, one at a time,
* and converting each to a number, string, or boolean
* <li>those for reading characters from standard input, one at a time
* <li>those for reading lines from standard input, one at a time
* <li>those for reading a sequence of values of the same type from standard input,
* and returning the values in an array
* </ul>
* <p>
* Generally, it is best not to mix functions from the different
* categories in the same program.
* <p>
* <b>Getting started.</b>
* To use this class, you must have {@code StdIn.class} in your
* Java classpath. If you used our autoinstaller, you should be all set.
* Otherwise, either download
* <a href = "https://introcs.cs.princeton.edu/java/code/stdlib.jar">stdlib.jar</a>
* and add to your Java classpath or download
* <a href = "https://introcs.cs.princeton.edu/java/stdlib/StdIn.java">StdIn.java</a>
* and put a copy in your working directory.
* <p>
* <b>Reading tokens from standard input and converting to numbers and strings.</b>
* You can use the following methods to read numbers, strings, and booleans
* from standard input one at a time:
* <ul>
* <li> {@link #isEmpty()}
* <li> {@link #readInt()}
* <li> {@link #readDouble()}
* <li> {@link #readString()}
* <li> {@link #readShort()}
* <li> {@link #readLong()}
* <li> {@link #readFloat()}
* <li> {@link #readByte()}
* <li> {@link #readBoolean()}
* </ul>
* <p>
* The first method returns true if standard input has no more tokens.
* Each other method skips over any input that is whitespace. Then, it reads
* the next token and attempts to convert it into a value of the specified
* type. If it succeeds, it returns that value; otherwise, it
* throws an {@link InputMismatchException}.
* <p>
* <em>Whitespace</em> includes spaces, tabs, and newlines; the full definition
* is inherited from {@link Character#isWhitespace(char)}.
* A <em>token</em> is a maximal sequence of non-whitespace characters.
* The precise rules for describing which tokens can be converted to
* integers and floating-point numbers are inherited from
* <a href = "http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#number-syntax">Scanner</a>,
* using the locale {@link Locale#US}; the rules
* for floating-point numbers are slightly different
* from those in {@link Double#valueOf(String)},
* but unlikely to be of concern to most programmers.
* <p>
* As an example, the following code fragment reads integers from standard input,
* one at a time, and prints them one per line.
* <pre>
* while (!StdIn.isEmpty()) {
* double value = StdIn.readDouble();
* StdOut.println(value);
* }
* </pre>
* <p>
* <b>Reading characters from standard input.</b>
* You can use the following two methods to read characters from standard input one at a time:
* <ul>
* <li> {@link #hasNextChar()}
* <li> {@link #readChar()}
* </ul>
* <p>
* The first method returns true if standard input has more input (including whitespace).
* The second method reads and returns the next character of input on standard
* input (possibly a whitespace character).
* <p>
* As an example, the following code fragment reads characters from standard input,
* one character at a time, and prints it to standard output.
* <pre>
* while (StdIn.hasNextChar()) {
* char c = StdIn.readChar();
* StdOut.print(c);
* }
* </pre>
* <p>
* <b>Reading lines from standard input.</b>
* You can use the following two methods to read lines from standard input:
* <ul>
* <li> {@link #hasNextLine()}
* <li> {@link #readLine()}
* </ul>
* <p>
* The first method returns true if standard input has more input (including whitespace).
* The second method reads and returns the remaining portion of
* the next line of input on standard input (possibly whitespace),
* discarding the trailing line separator.
* <p>
* A <em>line separator</em> is defined to be one of the following strings:
* {@code \n} (Linux), {@code \r} (old Macintosh),
* {@code \r\n} (Windows),
* {@code \}{@code u2028}, {@code \}{@code u2029}, or {@code \}{@code u0085}.
* <p>
* As an example, the following code fragment reads text from standard input,
* one line at a time, and prints it to standard output.
* <pre>
* while (StdIn.hasNextLine()) {
* String line = StdIn.readLine();
* StdOut.println(line);
* }
* </pre>
* <p>
* <b>Reading a sequence of values of the same type from standard input.</b>
* You can use the following methods to read a sequence numbers, strings,
* or booleans (all of the same type) from standard input:
* <ul>
* <li> {@link #readAllDoubles()}
* <li> {@link #readAllInts()}
* <li> {@link #readAllLongs()}
* <li> {@link #readAllStrings()}
* <li> {@link #readAllLines()}
* <li> {@link #readAll()}
* </ul>
* <p>
* The first three methods read of all of remaining token on standard input
* and converts the tokens to values of
* the specified type, as in the corresponding
* {@code readDouble}, {@code readInt}, and {@code readString()} methods.
* The {@code readAllLines()} method reads all remaining lines on standard
* input and returns them as an array of strings.
* The {@code readAll()} method reads all remaining input on standard
* input and returns it as a string.
* <p>
* As an example, the following code fragment reads all of the remaining
* tokens from standard input and returns them as an array of strings.
* <pre>
* String[] words = StdIn.readAllStrings();
* </pre>
* <p>
* <b>Differences with Scanner.</b>
* {@code StdIn} and {@link Scanner} are both designed to parse
* tokens and convert them to primitive types and strings.
* The main differences are summarized below:
* <ul>
* <li> {@code StdIn} is a set of static methods and reads
* reads input from only standard input. It is suitable for use before
* a programmer knows about objects.
* See {@link In} for an object-oriented version that handles
* input from files, URLs,
* and sockets.
* <li> {@code StdIn} uses whitespace as the delimiter pattern
* that separates tokens.
* {@link Scanner} supports arbitrary delimiter patterns.
* <li> {@code StdIn} coerces the character-set encoding to UTF-8,
* which is the most widely used character encoding for Unicode.
* <li> {@code StdIn} coerces the locale to {@link Locale#US},
* for consistency with {@link StdOut}, {@link Double#parseDouble(String)},
* and floating-point literals.
* <li> {@code StdIn} has convenient methods for reading a single
* character; reading in sequences of integers, doubles, or strings;
* and reading in all of the remaining input.
* </ul>
* <p>
* Historical note: {@code StdIn} preceded {@code Scanner}; when
* {@code Scanner} was introduced, this class was re-implemented to use {@code Scanner}.
* <p>
* <b>Using standard input.</b>
* Standard input is a fundamental operating system abstraction on Mac OS X,
* Windows, and Linux.
* The methods in {@code StdIn} are <em>blocking</em>, which means that they
* will wait until you enter input on standard input.
* If your program has a loop that repeats until standard input is empty,
* you must signal that the input is finished.
* To do so, depending on your operating system and IDE,
* use either {@code <Ctrl-d>} or {@code <Ctrl-z>}, on its own line.
* If you are redirecting standard input from a file, you will not need
* to do anything to signal that the input is finished.
* <p>
* <b>Known bugs.</b>
* Java's UTF-8 encoding does not recognize the optional
* <a href = "http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4508058">byte-order mask</a>.
* If the input begins with the optional byte-order mask, {@code StdIn}
* will have an extra character {@code \}{@code uFEFF} at the beginning.
* <p>
* <b>Reference.</b>
* For additional documentation,
* see <a href="https://introcs.cs.princeton.edu/15inout">Section 1.5</a> of
* <em>Computer Science: An Interdisciplinary Approach</em>
* by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
* @author David Pritchard
*/
public final class StdIn {
/*** 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 significant
private static final Pattern EMPTY_PATTERN = Pattern.compile("");
// used to read the entire input
private static final Pattern EVERYTHING_PATTERN = Pattern.compile("\\A");
/*** end: section (1 of 2) of code duplicated from In to StdIn. */
private static Scanner scanner;
// it doesn't make sense to instantiate this class
private StdIn() { }
//// begin: section (2 of 2) of code duplicated from In to StdIn,
//// with all methods changed from "public" to "public static"
/**
* Returns true if standard input is empty (except possibly for whitespace).
* Use this method to know whether the next call to {@link #readString()},
* {@link #readDouble()}, etc will succeed.
*
* @return {@code true} if standard input is empty (except possibly
* for whitespace); {@code false} otherwise
*/
public static boolean isEmpty() {
return !scanner.hasNext();
}
/**
* Returns true if standard input 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 {@code true} if standard input has more input (including whitespace);
* {@code false} otherwise
*/
public static boolean hasNextLine() {
return scanner.hasNextLine();
}
/**
* Returns true if standard input has more input (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 {@code true} if standard input has more input (including whitespace);
* {@code false} otherwise
*/
public static boolean hasNextChar() {
scanner.useDelimiter(EMPTY_PATTERN);
boolean result = scanner.hasNext();
scanner.useDelimiter(WHITESPACE_PATTERN);
return result;
}
/**
* Reads and returns the next line, excluding the line separator if present.
*
* @return the next line, excluding the line separator if present;
* {@code null} if no such line
*/
public static String readLine() {
String line;
try {
line = scanner.nextLine();
}
catch (NoSuchElementException e) {
line = null;
}
return line;
}
/**
* Reads and returns the next character.
*
* @return the next {@code char}
* @throws NoSuchElementException if standard input is empty
*/
public static char readChar() {
try {
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);
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attempts to read a 'char' value from standard input, "
+ "but no more tokens are available");
}
}
/**
* Reads and returns the remainder of the input, as a string.
*
* @return the remainder of the input, as a string
* @throws NoSuchElementException if standard input is empty
*/
public static 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 standard input and returns it as a {@code String}.
*
* @return the next {@code String}
* @throws NoSuchElementException if standard input is empty
*/
public static String readString() {
try {
return scanner.next();
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attempts to read a 'String' value from standard input, "
+ "but no more tokens are available");
}
}
/**
* Reads the next token from standard input, parses it as an integer, and returns the integer.
*
* @return the next integer on standard input
* @throws NoSuchElementException if standard input is empty
* @throws InputMismatchException if the next token cannot be parsed as an {@code int}
*/
public static int readInt() {
try {
return scanner.nextInt();
}
catch (InputMismatchException e) {
String token = scanner.next();
throw new InputMismatchException("attempts to read an 'int' value from standard input, "
+ "but the next token is \"" + token + "\"");
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attemps to read an 'int' value from standard input, "
+ "but no more tokens are available");
}
}
/**
* Reads the next token from standard input, parses it as a double, and returns the double.
*
* @return the next double on standard input
* @throws NoSuchElementException if standard input is empty
* @throws InputMismatchException if the next token cannot be parsed as a {@code double}
*/
public static double readDouble() {
try {
return scanner.nextDouble();
}
catch (InputMismatchException e) {
String token = scanner.next();
throw new InputMismatchException("attempts to read a 'double' value from standard input, "
+ "but the next token is \"" + token + "\"");
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attempts to read a 'double' value from standard input, "
+ "but no more tokens are available");
}
}
/**
* Reads the next token from standard input, parses it as a float, and returns the float.
*
* @return the next float on standard input
* @throws NoSuchElementException if standard input is empty
* @throws InputMismatchException if the next token cannot be parsed as a {@code float}
*/
public static float readFloat() {
try {
return scanner.nextFloat();
}
catch (InputMismatchException e) {
String token = scanner.next();
throw new InputMismatchException("attempts to read a 'float' value from standard input, "
+ "but the next token is \"" + token + "\"");
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attempts to read a 'float' value from standard input, "
+ "but there no more tokens are available");
}
}
/**
* Reads the next token from standard input, parses it as a long integer, and returns the long integer.
*
* @return the next long integer on standard input
* @throws NoSuchElementException if standard input is empty
* @throws InputMismatchException if the next token cannot be parsed as a {@code long}
*/
public static long readLong() {
try {
return scanner.nextLong();
}
catch (InputMismatchException e) {
String token = scanner.next();
throw new InputMismatchException("attempts to read a 'long' value from standard input, "
+ "but the next token is \"" + token + "\"");
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attempts to read a 'long' value from standard input, "
+ "but no more tokens are available");
}
}
/**
* Reads the next token from standard input, parses it as a short integer, and returns the short integer.
*
* @return the next short integer on standard input
* @throws NoSuchElementException if standard input is empty
* @throws InputMismatchException if the next token cannot be parsed as a {@code short}
*/
public static short readShort() {
try {
return scanner.nextShort();
}
catch (InputMismatchException e) {
String token = scanner.next();
throw new InputMismatchException("attempts to read a 'short' value from standard input, "
+ "but the next token is \"" + token + "\"");
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attempts to read a 'short' value from standard input, "
+ "but no more tokens are available");
}
}
/**
* Reads the next token from standard input, parses it as a byte, and returns the byte.
*
* @return the next byte on standard input
* @throws NoSuchElementException if standard input is empty
* @throws InputMismatchException if the next token cannot be parsed as a {@code byte}
*/
public static byte readByte() {
try {
return scanner.nextByte();
}
catch (InputMismatchException e) {
String token = scanner.next();
throw new InputMismatchException("attempts to read a 'byte' value from standard input, "
+ "but the next token is \"" + token + "\"");
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attempts to read a 'byte' value from standard input, "
+ "but no more tokens are available");
}
}
/**
* Reads the next token from standard input, parses it as a boolean,
* and returns the boolean.
*
* @return the next boolean on standard input
* @throws NoSuchElementException if standard input is empty
* @throws InputMismatchException if the next token cannot be parsed as a {@code boolean}:
* {@code true} or {@code 1} for true, and {@code false} or {@code 0} for false,
* ignoring case
*/
public static boolean readBoolean() {
try {
String token = readString();
if ("true".equalsIgnoreCase(token)) return true;
if ("false".equalsIgnoreCase(token)) return false;
if ("1".equals(token)) return true;
if ("0".equals(token)) return false;
throw new InputMismatchException("attempts to read a 'boolean' value from standard input, "
+ "but the next token is \"" + token + "\"");
}
catch (NoSuchElementException e) {
throw new NoSuchElementException("attempts to read a 'boolean' value from standard input, "
+ "but no more tokens are available");
}
}
/**
* Reads all remaining tokens from standard input and returns them as an array of strings.
*
* @return all remaining tokens on standard input, as an array of strings
*/
public static String[] readAllStrings() {
// we could use readAll.trim().split(), but that's not consistent
// because trim() uses characters 0x00..0x20 as whitespace
String[] tokens = WHITESPACE_PATTERN.split(readAll());
if (tokens.length == 0 || tokens[0].length() > 0)
return tokens;
// don't include first token if it is leading whitespace
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 standard input and returns them as an array of strings.
* @return all remaining lines on standard input, as an array of strings
*/
public static String[] readAllLines() {
ArrayList<String> lines = new ArrayList<String>();
while (hasNextLine()) {
lines.add(readLine());
}
return lines.toArray(new String[lines.size()]);
}
/**
* Reads all remaining tokens from standard input, parses them as integers, and returns
* them as an array of integers.
* @return all remaining integers on standard input, as an array
* @throws InputMismatchException if any token cannot be parsed as an {@code int}
*/
public static 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 standard input, parses them as longs, and returns
* them as an array of longs.
* @return all remaining longs on standard input, as an array
* @throws InputMismatchException if any token cannot be parsed as a {@code long}
*/
public static long[] readAllLongs() {
String[] fields = readAllStrings();
long[] vals = new long[fields.length];
for (int i = 0; i < fields.length; i++)
vals[i] = Long.parseLong(fields[i]);
return vals;
}
/**
* Reads all remaining tokens from standard input, parses them as doubles, and returns
* them as an array of doubles.
* @return all remaining doubles on standard input, as an array
* @throws InputMismatchException if any token cannot be parsed as a {@code double}
*/
public static 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
// do this once when StdIn is initialized
static {
resync();
}
/**
* If StdIn changes, use this to reinitialize the scanner.
*/
private static void resync() {
setScanner(new Scanner(new java.io.BufferedInputStream(System.in), CHARSET_NAME));
}
private static void setScanner(Scanner scanner) {
StdIn.scanner = scanner;
StdIn.scanner.useLocale(LOCALE);
}
/**
* Reads all remaining tokens, parses them as integers, and returns
* them as an array of integers.
* @return all remaining integers, as an array
* @throws InputMismatchException if any token cannot be parsed as an {@code int}
* @deprecated Replaced by {@link #readAllInts()}.
*/
@Deprecated
public static int[] readInts() {
return readAllInts();
}
/**
* Reads all remaining tokens, parses them as doubles, and returns
* them as an array of doubles.
* @return all remaining doubles, as an array
* @throws InputMismatchException if any token cannot be parsed as a {@code double}
* @deprecated Replaced by {@link #readAllDoubles()}.
*/
@Deprecated
public static double[] readDoubles() {
return readAllDoubles();
}
/**
* Reads all remaining tokens and returns them as an array of strings.
* @return all remaining tokens, as an array of strings
* @deprecated Replaced by {@link #readAllStrings()}.
*/
@Deprecated
public static String[] readStrings() {
return readAllStrings();
}
/**
* Interactive test of basic functionality.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
StdOut.print("Type a string: ");
String s = StdIn.readString();
StdOut.println("Your string was: " + s);
StdOut.println();
StdOut.print("Type an int: ");
int a = StdIn.readInt();
StdOut.println("Your int was: " + a);
StdOut.println();
StdOut.print("Type a boolean: ");
boolean b = StdIn.readBoolean();
StdOut.println("Your boolean was: " + b);
StdOut.println();
StdOut.print("Type a double: ");
double c = StdIn.readDouble();
StdOut.println("Your double was: " + c);
StdOut.println();
}
}
/******************************************************************************
* Copyright 2002-2020, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4.jar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* algs4.jar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with algs4.jar. If not, see http://www.gnu.org/licenses.
******************************************************************************/
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