Scanner skip java что это
Сканер skip () метод в Java с примерами
пропустить (Pattern Pattern)
Метод skip (Pattern pattern) класса java.util.Scanner пропускает ввод, соответствующий указанному шаблону, игнорируя разделители. Функция пропускает ввод, если закрепленное соответствие указанного шаблона следует за ним.
Синтаксис:
Параметры: функция принимает обязательный шаблон параметров , который задает строку как шаблон, который должен быть пропущен.
Возвращаемое значение: функция возвращает этот сканер
Исключения: этот метод генерирует следующие исключения:
Ниже программы иллюстрируют вышеуказанную функцию:
Программа 1:
// Java-программа для иллюстрации
// метод skip () класса Scanner в Java
public static void main(String[] argv)
+ «A Computer Science Portal for Geeks» ;
System.out.println( «String trying to get input:\n»
// создаем новый сканер с
// указанный объект String
Scanner scanner = new Scanner(s);
// пропустить слово, которое
System.out.println( «Skipping 5 letter words»
+ » that ends with ‘eks’\n» );
// выводим строку сканера
System.out.println( «Input Scanner String: \n»
Программа 2: продемонстрировать исключение NoSuchElementException
// Java-программа для иллюстрации
// метод skip () класса Scanner в Java
public static void main(String[] argv)
+ «A Computer Science Portal for Geeks» ;
System.out.println( «String trying to get input:\n»
// создаем новый сканер с
// указанный объект String
Scanner scanner = new Scanner(s);
// пропустить слово, которое
// соответствует шаблону и
System.out.println( «Skipping 3 letter words»
// выводим строку сканера
System.out.println( «Input Scanner String: \n»
System.out.println( «Exception thrown: » + e);
Программа 3: продемонстрировать IllegalStateException
// Java-программа для иллюстрации
// метод skip () класса Scanner в Java
public static void main(String[] argv)
+ «A Computer Science Portal for Geeks» ;
System.out.println( «String trying to get input:\n»
// создаем новый сканер с
// указанный объект String
Scanner scanner = new Scanner(s);
System.out.println( «Scanner Closed» );
// пропустить слово, которое
// соответствует шаблону и
System.out.println( «Trying to Skip 3 letter words»
// выводим строку сканера
System.out.println( «Input Scanner String: \n»
System.out.println( «Exception thrown: » + e);
пропустить (образец строки)
Метод skip (String pattern) класса java.util.Scanner пропускает ввод, соответствующий шаблону, созданному из указанной строки. Пропуск (pattern) и skip (Pattern.compile (pattern)) ведут себя точно так же при вызове.
Синтаксис:
Параметры: функция принимает обязательный шаблон строки параметров, который указывает строку, обозначающую шаблон, который необходимо пропустить
Возвращаемое значение: функция возвращает этот сканер
Исключения: этот метод создает исключение IllegalStateException при закрытии этого сканера.
Ниже программы иллюстрируют вышеуказанную функцию:
Программа 1:
// Java-программа для иллюстрации
// метод skip () класса Scanner в Java
public static void main(String[] argv)
+ «A Computer Science Portal for Geeks» ;
System.out.println( «String trying to get input:\n»
// создаем новый сканер с
// указанный объект String
Scanner scanner = new Scanner(s);
// пропустить слово, которое
System.out.println( «Skipping 5 letter words»
+ » that ends with ‘eks’\n» );
// выводим строку сканера
System.out.println( «Input Scanner String: \n»
Программа 2: продемонстрировать IllegalStateException
// Java-программа для иллюстрации
// метод skip () класса Scanner в Java
Что сканер пропускает в Java и зачем его использовать?
2 ответа
Пропускает ввод, соответствующий указанному шаблону, игнорируя разделители. Этот метод пропускает ввод, если привязка соответствия указанного шаблона завершается успешно. Если совпадение с указанным шаблоном не найдено в текущей позиции, то ни один вход не пропускается и не генерируется исключение NoSuchElementException.
Поскольку этот метод пытается совместить указанный шаблон, начиная с текущего положения сканера, шаблоны который может соответствовать большому количеству входных данных (например, «. *»), может привести к тому, что сканер будет буферировать большой объем ввода.
Таким образом, это позволяет вам «перемещать» положение сканера используя регулярное выражение.
Пример:
Пропустить начало строки:
Поскольку это использует регулярное выражение, вы пропускаете до работы в середине строки:
Метод skip() этого класса делает именно это. Он пропустит вход, соответствующий шаблону. В этом случае шаблон говорит, чтобы пропускать возврат каретки (\r) и новые строки (\n), а также некоторые символы Unicode.
Итак, когда строка читается, она игнорирует этот шаблон и возвращает только остальную часть строки. Простым примером будет такой. Предположим, у вас есть строка:
String s = «Hello world, this is my scanner!»;
Тогда, если у вас есть сканер, например:
Затем, когда вы выполните:
Выход на консоль будет просто
Scanner skip java что это
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.
For example, this code allows a user to read a number from System.in:
As another example, this code allows long types to be assigned from entries in a file myNumbers :
The scanner can also use delimiters other than whitespace. This example reads several items in from a string:
prints the following output:
The same output can be generated with this code, which uses a regular expression to parse all four tokens at once:
A scanning operation may block waiting for input.
The next() and hasNext() methods and their primitive-type companion methods (such as nextInt() and hasNextInt() ) first skip any input that matches the delimiter pattern, and then attempt to return the next token. Both hasNext and next methods may block waiting for further input. Whether a hasNext method blocks has no connection to whether or not its associated next method will block.
Depending upon the type of delimiting pattern, empty tokens may be returned. For example, the pattern "\\s+" will return no empty tokens since it matches multiple instances of the delimiter. The delimiting pattern "\\s" could return empty tokens since it only passes one space at a time.
A scanner can read text from any object which implements the Readable interface. If an invocation of the underlying readable’s Readable.read(java.nio.CharBuffer) method throws an IOException then the scanner assumes that the end of the input has been reached. The most recent IOException thrown by the underlying readable can be retrieved via the ioException() method.
When a Scanner is closed, it will close its input source if the source implements the Closeable interface.
A Scanner is not safe for multithreaded use without external synchronization.
Unless otherwise mentioned, passing a null parameter into any method of a Scanner will cause a NullPointerException to be thrown.
A scanner will default to interpreting numbers as decimal unless a different radix has been set by using the useRadix(int) method. The reset() method will reset the value of the scanner’s radix to 10 regardless of whether it was previously changed.
Localized numbers
An instance of this class is capable of scanning numbers in the standard formats as well as in the formats of the scanner’s locale. A scanner’s initial locale is the value returned by the Locale.getDefault() method; it may be changed via the useLocale(java.util.Locale) method. The reset() method will reset the value of the scanner’s locale to the initial locale regardless of whether it was previously changed.
The localized formats are defined in terms of the following parameters, which for a particular locale are taken from that locale’s DecimalFormat object, df, and its and DecimalFormatSymbols object, dfs.
LocalGroupSeparator The character used to separate thousands groups, i.e., dfs. getGroupingSeparator() LocalDecimalSeparator The character used for the decimal point, i.e., dfs. getDecimalSeparator() LocalPositivePrefix The string that appears before a positive number (may be empty), i.e., df. getPositivePrefix() LocalPositiveSuffix The string that appears after a positive number (may be empty), i.e., df. getPositiveSuffix() LocalNegativePrefix The string that appears before a negative number (may be empty), i.e., df. getNegativePrefix() LocalNegativeSuffix The string that appears after a negative number (may be empty), i.e., df. getNegativeSuffix() LocalNaN The string that represents not-a-number for floating-point values, i.e., dfs. getNaN() LocalInfinity The string that represents infinity for floating-point values, i.e., dfs. getInfinity()
Number syntax
The strings that can be parsed as numbers by an instance of this class are specified in terms of the following regular-expression grammar, where Rmax is the highest digit in the radix being used (for example, Rmax is 9 in base 10).
| NonASCIIDigit :: | = A non-ASCII character c for which Character.isDigit (c) returns true | |||
| Non0Digit :: | = [1-Rmax] | NonASCIIDigit | |||
| Digit :: | = [0-Rmax] | NonASCIIDigit | |||
| GroupedNumeral :: |
| |||
| Numeral :: | = ( ( Digit+ ) | GroupedNumeral ) | |||
| Integer :: | = ( [-+]? ( Numeral ) ) | |||
| | LocalPositivePrefix Numeral LocalPositiveSuffix | ||||
| | LocalNegativePrefix Numeral LocalNegativeSuffix | ||||
| DecimalNumeral :: | = Numeral | |||
| | Numeral LocalDecimalSeparator Digit* | ||||
| | LocalDecimalSeparator Digit+ | ||||
| Exponent :: | = ( [eE] [+-]? Digit+ ) | |||
| Decimal :: | = ( [-+]? DecimalNumeral Exponent? ) | |||
| | LocalPositivePrefix DecimalNumeral LocalPositiveSuffix Exponent? | ||||
| | LocalNegativePrefix DecimalNumeral LocalNegativeSuffix Exponent? | ||||
| HexFloat :: | = [-+]? 0[xX][0-9a-fA-F]*\.[0-9a-fA-F]+ ([pP][-+]?9+)? | |||
| NonNumber :: | = NaN | LocalNan | Infinity | LocalInfinity | |||
| SignedNonNumber :: | = ( [-+]? NonNumber ) | |||
| | LocalPositivePrefix NonNumber LocalPositiveSuffix | ||||
| | LocalNegativePrefix NonNumber LocalNegativeSuffix | ||||
| Float :: | = Decimal | |||
| | HexFloat | ||||
| | SignedNonNumber |
Whitespace is not significant in the above regular expressions.
Constructor Summary
Method Summary
| Modifier and Type | Method and Description |
|---|---|
| void | close() |
Methods inherited from class java.lang.Object
Constructor Detail
Scanner
Scanner
Scanner
Scanner
Scanner
Scanner
Scanner
Scanner
Scanner
Scanner
Method Detail
close
If this scanner has not yet been closed then if its underlying readable also implements the Closeable interface then the readable's close method will be invoked. If this scanner is already closed then invoking this method will have no effect.
ioException
delimiter
useDelimiter
useDelimiter
An invocation of this method of the form useDelimiter(pattern) behaves in exactly the same way as the invocation useDelimiter(Pattern.compile(pattern)).
Invoking the reset() method will set the scanner's delimiter to the default.
locale
A scanner's locale affects many elements of its default primitive matching regular expressions; see localized numbers above.
useLocale
A scanner's locale affects many elements of its default primitive matching regular expressions; see localized numbers above.
Invoking the reset() method will set the scanner's locale to the initial locale.
radix
A scanner's radix affects elements of its default number matching regular expressions; see localized numbers above.
useRadix
A scanner's radix affects elements of its default number matching regular expressions; see localized numbers above.
match
toString
hasNext
remove
hasNext
An invocation of this method of the form hasNext(pattern) behaves in exactly the same way as the invocation hasNext(Pattern.compile(pattern)).
An invocation of this method of the form next(pattern) behaves in exactly the same way as the invocation next(Pattern.compile(pattern)).
hasNext
hasNextLine
nextLine
Since this method continues to search through the input looking for a line separator, it may buffer all of the input searching for the line to skip if no line separators are present.
findInLine
An invocation of this method of the form findInLine(pattern) behaves in exactly the same way as the invocation findInLine(Pattern.compile(pattern)).
findInLine
Since this method continues to search through the input looking for the specified pattern, it may buffer all of the input searching for the desired token if no line separators are present.
findWithinHorizon
An invocation of this method of the form findWithinHorizon(pattern) behaves in exactly the same way as the invocation findWithinHorizon(Pattern.compile(pattern, horizon)).
findWithinHorizon
This method searches through the input up to the specified search horizon, ignoring delimiters. If the pattern is found the scanner advances past the input that matched and returns the string that matched the pattern. If no such pattern is detected then the null is returned and the scanner's position remains unchanged. This method may block waiting for input that matches the pattern.
A scanner will never search more than horizon code points beyond its current position. Note that a match may be clipped by the horizon; that is, an arbitrary match result may have been different if the horizon had been larger. The scanner treats the horizon as a transparent, non-anchoring bound (see Matcher.useTransparentBounds(boolean) and Matcher.useAnchoringBounds(boolean) ).
If horizon is negative, then an IllegalArgumentException is thrown.
If a match to the specified pattern is not found at the current position, then no input is skipped and a NoSuchElementException is thrown.
Since this method seeks to match the specified pattern starting at the scanner's current position, patterns that can match a lot of input (".*", for example) may cause the scanner to buffer a large amount of input.
An invocation of this method of the form skip(pattern) behaves in exactly the same way as the invocation skip(Pattern.compile(pattern)).
hasNextBoolean
nextBoolean
hasNextByte
hasNextByte
nextByte
An invocation of this method of the form nextByte() behaves in exactly the same way as the invocation nextByte(radix), where radix is the default radix of this scanner.
nextByte
hasNextShort
hasNextShort
nextShort
An invocation of this method of the form nextShort() behaves in exactly the same way as the invocation nextShort(radix), where radix is the default radix of this scanner.
nextShort
hasNextInt
hasNextInt
nextInt
An invocation of this method of the form nextInt() behaves in exactly the same way as the invocation nextInt(radix), where radix is the default radix of this scanner.
nextInt
hasNextLong
hasNextLong
nextLong
An invocation of this method of the form nextLong() behaves in exactly the same way as the invocation nextLong(radix), where radix is the default radix of this scanner.
nextLong
hasNextFloat
nextFloat
hasNextDouble
nextDouble
hasNextBigInteger
hasNextBigInteger
nextBigInteger
An invocation of this method of the form nextBigInteger() behaves in exactly the same way as the invocation nextBigInteger(radix), where radix is the default radix of this scanner.
nextBigInteger
hasNextBigDecimal
nextBigDecimal
reset
An invocation of this method of the form scanner.reset() behaves in exactly the same way as the invocation
Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2020, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
Scanner skip java что это
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.
For example, this code allows a user to read a number from System.in:
As another example, this code allows long types to be assigned from entries in a file myNumbers :
The scanner can also use delimiters other than whitespace. This example reads several items in from a string:
prints the following output:
The same output can be generated with this code, which uses a regular expression to parse all four tokens at once:
A scanning operation may block waiting for input.
The next() and hasNext() methods and their primitive-type companion methods (such as nextInt() and hasNextInt() ) first skip any input that matches the delimiter pattern, and then attempt to return the next token. Both hasNext and next methods may block waiting for further input. Whether a hasNext method blocks has no connection to whether or not its associated next method will block.
Depending upon the type of delimiting pattern, empty tokens may be returned. For example, the pattern "\\s+" will return no empty tokens since it matches multiple instances of the delimiter. The delimiting pattern "\\s" could return empty tokens since it only passes one space at a time.
A scanner can read text from any object which implements the Readable interface. If an invocation of the underlying readable's Readable.read(java.nio.CharBuffer) method throws an IOException then the scanner assumes that the end of the input has been reached. The most recent IOException thrown by the underlying readable can be retrieved via the ioException() method.
When a Scanner is closed, it will close its input source if the source implements the Closeable interface.
A Scanner is not safe for multithreaded use without external synchronization.
Unless otherwise mentioned, passing a null parameter into any method of a Scanner will cause a NullPointerException to be thrown.
A scanner will default to interpreting numbers as decimal unless a different radix has been set by using the useRadix(int) method. The reset() method will reset the value of the scanner's radix to 10 regardless of whether it was previously changed.
Localized numbers
An instance of this class is capable of scanning numbers in the standard formats as well as in the formats of the scanner's locale. A scanner's initial locale is the value returned by the Locale.getDefault(Locale.Category.FORMAT) method; it may be changed via the useLocale(java.util.Locale) method. The reset() method will reset the value of the scanner's locale to the initial locale regardless of whether it was previously changed.
The localized formats are defined in terms of the following parameters, which for a particular locale are taken from that locale's DecimalFormat object, df, and its and DecimalFormatSymbols object, dfs.
LocalGroupSeparator The character used to separate thousands groups, i.e., dfs. getGroupingSeparator() LocalDecimalSeparator The character used for the decimal point, i.e., dfs. getDecimalSeparator() LocalPositivePrefix The string that appears before a positive number (may be empty), i.e., df. getPositivePrefix() LocalPositiveSuffix The string that appears after a positive number (may be empty), i.e., df. getPositiveSuffix() LocalNegativePrefix The string that appears before a negative number (may be empty), i.e., df. getNegativePrefix() LocalNegativeSuffix The string that appears after a negative number (may be empty), i.e., df. getNegativeSuffix() LocalNaN The string that represents not-a-number for floating-point values, i.e., dfs. getNaN() LocalInfinity The string that represents infinity for floating-point values, i.e., dfs. getInfinity()
Number syntax
The strings that can be parsed as numbers by an instance of this class are specified in terms of the following regular-expression grammar, where Rmax is the highest digit in the radix being used (for example, Rmax is 9 in base 10). NonAsciiDigit: A non-ASCII character c for which Character.isDigit (c) returns true Non0Digit: [1-Rmax] | NonASCIIDigit Digit: [0-Rmax] | NonASCIIDigit GroupedNumeral: ( Non0Digit Digit? Digit? ( LocalGroupSeparator Digit Digit Digit )+ ) Numeral: ( ( Digit+ ) | GroupedNumeral ) Integer: ( [-+]? ( Numeral ) ) | LocalPositivePrefix Numeral LocalPositiveSuffix | LocalNegativePrefix Numeral LocalNegativeSuffix DecimalNumeral: Numeral | Numeral LocalDecimalSeparator Digit* | LocalDecimalSeparator Digit+ Exponent: ( [eE] [+-]? Digit+ ) Decimal: ( [-+]? DecimalNumeral Exponent? ) | LocalPositivePrefix DecimalNumeral LocalPositiveSuffix Exponent? | LocalNegativePrefix DecimalNumeral LocalNegativeSuffix Exponent? HexFloat: [-+]? 0[xX][0-9a-fA-F]*\.[0-9a-fA-F]+ ([pP][-+]?4+)? NonNumber: NaN | LocalNan | Infinity | LocalInfinity SignedNonNumber: ( [-+]? NonNumber ) | LocalPositivePrefix NonNumber LocalPositiveSuffix | LocalNegativePrefix NonNumber LocalNegativeSuffix Float: Decimal | HexFloat | SignedNonNumber
Whitespace is not significant in the above regular expressions.