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StdIn.java
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487 lines (434 loc) · 16.9 KB
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package com.wang.code.utils;
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;
/**
* @author WANGJJ
* @date 2020/04/15
*/
public 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 and returns the {@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();
}
}