Scanner close java

Scanner close() method in Java with Examples

The close() method ofjava.util.Scanner class closes the scanner which has been opened. If the scanner is already closed then on calling this method, it will have no effect.

Syntax:

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public void close()

Return Value: The function does not return any value.

Below programs illustrate the above function:

Program 1:

Output: Scanner: Geeksforgeeks has Scanner Class Methods Scanner Closed. Trying to use scanner after closing. Exception thrown: java.lang.IllegalStateException: Scanner closed

Reference:https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#close()

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Sours: https://www.geeksforgeeks.org/scanner-close-method-in-java-with-examples/

Modifier and TypeMethod and Description

Closes this scanner.

Returns the this is currently using to match delimiters.

Attempts to find the next occurrence of the specified pattern ignoring delimiters.

Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.

Attempts to find the next occurrence of the specified pattern.

Attempts to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.

Returns true if this scanner has another token in its input.

Returns true if the next complete token matches the specified pattern.

Returns true if the next token matches the pattern constructed from the specified string.

Returns true if the next token in this scanner's input can be interpreted as a using the method.

Returns true if the next token in this scanner's input can be interpreted as a in the default radix using the method.

Returns true if the next token in this scanner's input can be interpreted as a in the specified radix using the method.

Returns true if the next token in this scanner's input can be interpreted as a boolean value using a case insensitive pattern created from the string "true|false".

Returns true if the next token in this scanner's input can be interpreted as a byte value in the default radix using the method.

Returns true if the next token in this scanner's input can be interpreted as a byte value in the specified radix using the method.

Returns true if the next token in this scanner's input can be interpreted as a double value using the method.

Returns true if the next token in this scanner's input can be interpreted as a float value using the method.

Returns true if the next token in this scanner's input can be interpreted as an int value in the default radix using the method.

Returns true if the next token in this scanner's input can be interpreted as an int value in the specified radix using the method.

Returns true if there is another line in the input of this scanner.

Returns true if the next token in this scanner's input can be interpreted as a long value in the default radix using the method.

Returns true if the next token in this scanner's input can be interpreted as a long value in the specified radix using the method.

Returns true if the next token in this scanner's input can be interpreted as a short value in the default radix using the method.

Returns true if the next token in this scanner's input can be interpreted as a short value in the specified radix using the method.

Returns the last thrown by this 's underlying .

Returns this scanner's locale.

Returns the match result of the last scanning operation performed by this scanner.

Finds and returns the next complete token from this scanner.

Returns the next token if it matches the specified pattern.

Returns the next token if it matches the pattern constructed from the specified string.

Scans the next token of the input as a .

Scans the next token of the input into a boolean value and returns that value.

Scans the next token of the input as a .

Scans the next token of the input as an .

Advances this scanner past the current line and returns the input that was skipped.

Scans the next token of the input as a .

Returns this scanner's default radix.

The remove operation is not supported by this implementation of .

Resets this scanner.

Skips input that matches the specified pattern, ignoring delimiters.

Skips input that matches a pattern constructed from the specified string.

Returns the string representation of this .

Sets this scanner's delimiting pattern to the specified pattern.

Sets this scanner's delimiting pattern to a pattern constructed from the specified .

Sets this scanner's locale to the specified locale.

Sets this scanner's default radix to the specified radix.

Sours: https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html

A simple text scanner which can parse primitive types and strings using regular expressions.

A 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 methods.

For example, this code allows a user to read a number from :

As another example, this code allows types to be assigned from entries in a file :

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:

The default whitespace delimiter used by a scanner is as recognized by .. The method will reset the value of the scanner's delimiter to the default whitespace delimiter regardless of whether it was previously changed.

A scanning operation may block waiting for input.

The and methods and their primitive-type companion methods (such as and ) first skip any input that matches the delimiter pattern, and then attempt to return the next token. Both and methods may block waiting for further input. Whether a method blocks has no connection to whether or not its associated method will block.

The , , and methods operate independently of the delimiter pattern. These methods will attempt to match the specified pattern with no regard to delimiters in the input and thus can be used in special circumstances where delimiters are not relevant. These methods may block waiting for more input.

When a scanner throws an , the scanner will not pass the token that caused the exception, so that it may be retrieved or skipped via some other method.

Depending upon the type of delimiting pattern, empty tokens may be returned. For example, the pattern will return no empty tokens since it matches multiple instances of the delimiter. The delimiting pattern could return empty tokens since it only passes one space at a time.

A scanner can read text from any object which implements the interface. If an invocation of the underlying readable's method throws an then the scanner assumes that the end of the input has been reached. The most recent thrown by the underlying readable can be retrieved via the method.

When a is closed, it will close its input source if the source implements the interface.

A is not safe for multithreaded use without external synchronization.

Unless otherwise mentioned, passing a parameter into any method of a will cause a to be thrown.

A scanner will default to interpreting numbers as decimal unless a different radix has been set by using the method. The method will reset the value of the scanner's radix to 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 method; it may be changed via the method. The 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 object, , and its and object, .

LocalGroupSeparator
The character used to separate thousands groups, i.e.,
LocalDecimalSeparator
The character used for the decimal point, i.e.,
LocalPositivePrefix
The string that appears before a positive number (may be empty), i.e.,
LocalPositiveSuffix
The string that appears after a positive number (may be empty), i.e.,
LocalNegativePrefix
The string that appears before a negative number (may be empty), i.e.,
LocalNegativeSuffix
The string that appears after a negative number (may be empty), i.e.,
LocalNaN
The string that represents not-a-number for floating-point values, i.e.,
LocalInfinity
The string that represents infinity for floating-point values, i.e.,

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 returns true
Non0Digit:: RmaxNonASCIIDigit
Digit:: RmaxNonASCIIDigit
GroupedNumeral:: Non0DigitDigitDigit; LocalGroupSeparatorDigitDigitDigit
Numeral:: DigitGroupedNumeral
Integer:: Numeral; LocalPositivePrefixNumeralLocalPositiveSuffix; LocalNegativePrefixNumeralLocalNegativeSuffix
DecimalNumeral:: Numeral; NumeralLocalDecimalSeparatorDigit; LocalDecimalSeparatorDigit
Exponent:: Digit
Decimal:: DecimalNumeralExponent; LocalPositivePrefixDecimalNumeralLocalPositiveSuffixExponent; LocalNegativePrefixDecimalNumeralLocalNegativeSuffixExponent
HexFloat:
NonNumber:: LocalNanLocalInfinity
SignedNonNumber:: NonNumber; LocalPositivePrefixNonNumberLocalPositiveSuffix; LocalNegativePrefixNonNumberLocalNegativeSuffix
Float:: DecimalHexFloatSignedNonNumber

Whitespace is not significant in the above regular expressions.

Since:: 1.5

Sours: https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html

Import and Scanner in Java

Java.util.Scanner.close() Method

Description

The java.util.Scanner.close() method closes this scanner.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.

Declaration

Following is the declaration for java.util.Scanner.close() method

public void close()

Parameters

Return Value

This method does not return any value.

Exception

Example

The following example shows the usage of java.util.Scanner.close() method.

Live Demo

package com.tutorialspoint; import java.util.*; public class ScannerDemo { public static void main(String[] args) { String s = "Hello World! 3 + 3.0 = 6"; // create a new scanner with the specified String Object Scanner scanner = new Scanner(s); // print the next line of the string System.out.println("" + scanner.nextLine()); // close the scanner System.out.println("Closing Scanner..."); scanner.close(); System.out.println("Scanner Closed."); } }

Let us compile and run the above program, this will produce the following result −

Hello World! 3 + 3.0 = 6 Closing Scanner... Scanner Closed.

java_util_scanner.htm

Sours: https://www.tutorialspoint.com/java/util/scanner_close.htm

Close java scanner

Java Scanner close() Method

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The close() is a method of Java Scanner class which is used to closes this scanner.

Syntax

Following is the declaration of close() method:

Parameter

This method does not accept any parameter.

Returns

The close() method does not return any value.

Exceptions

Compatibility Version

Java 1.5 and above

Example 1

Output:

Hi All! This is JavaTpoint. Closing Scanner... Scanner Closed.

Example 2

Output:

Enter Your Name: JavaTpoint Name: JavaTpoint Scanner Closed.

Example 3

Output:

Throws Exception If Number is of Type Long. Enter your rollno: 345643985649356 Exception in thread "main" java.util.InputMismatchException: For input string: "345643985649356" at java.base/java.util.Scanner.nextInt(Scanner.java:2264) at java.base/java.util.Scanner.nextInt(Scanner.java:2212) at myPackage.ScannerCloseExample3.main(ScannerCloseExample3.java:9)

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The Scanner Class in Java

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Common ways to obtain Scanner

private void myMethod () {

}

Scanner scanner = null; try { scanner = newScanner(System.in); } finally { if(scanner!=null) scanner.close(); }

private String resolveEnvParams(Readable in) { Scanner s = newScanner(in).useDelimiter("\\A"); try { if (s.hasNext()) { return resolveEnvParams(s.next()); } return""; } finally { s.close(); } }

publicstatic List<Target> getTargetsFromFile(String LabFile, HMMData htsData) throws Exception { List<Target> targets = null; Scanner s = null; try { s = newScanner(new BufferedReader(new FileReader(LabFile))); targets = getTargets(s, htsData); } catch (FileNotFoundException e) { System.err.println("FileNotFoundException: " + e.getMessage()); } finally { if (s != null) s.close(); } return targets; }

publicvoid readShapeData() throws IOException { Scanner in = newScanner(System.in); try { System.out.println("Enter the width of the Rectangle: "); width = in.nextDouble(); System.out.println("Enter the height of the Rectangle: "); height = in.nextDouble(); } finally { in.close(); } }

Scanner sc = null; try { sc = newScanner( lastLine ); sc = sc.useDelimiter( "\\D+" ); int i = 0; sc.close(); return null; File errorFile = newFile( meta.getErrorFileName() ); if ( !errorFile.exists() ) { return null;

final Scanner scan = newScanner(newFile("/path/to/StudentsList")); final List<Student> students = new ArrayList<Student>(); while (scan.hasNextLine()) { final Scanner line = newScanner(scan.nextLine()); line.useDelimiter("%"); students.add(new Student(line.next(), line.nextInt(), line.nextInt())); line.close(); } scan.close();

privateint parseRevision( @Nonnull final String rawRevision ) throws InvalidRevisionException { if( !PATTERN_VALID_REVISION.matcher( rawRevision ).matches() ) { thrownew InvalidRevisionException(); } final Scanner scanner = newScanner( rawRevision ); finalint revision = scanner.useDelimiter( PATTERN_REVISION ).nextInt(); scanner.close(); return revision; }

Scanner scanner = newScanner( newFile("poem.txt") ); String text = scanner.useDelimiter("\\A").next(); scanner.close();

private String resolveEnvParams(Readable in) { Scanner s = newScanner(in).useDelimiter("\\A"); try { if (s.hasNext()) { return resolveEnvParams(s.next()); } return""; } finally { s.close(); } }

privatestatic String checkGpuAnalyzerVersion(){ try { ProcessBuilder pb = new ProcessBuilder("GPUShaderAnalyzer", "-ListModules"); Process p = pb.start(); Scanner scan = newScanner(p.getInputStream()); String ln = scan.nextLine(); scan.close(); p.destroy(); return ln; } catch (IOException ex) { logger.log(Level.SEVERE, "IOEx", ex); } return null; }

privateint parseBuild( @Nonnull final String rawBuild ) throws InvalidBuildException { if( !PATTERN_NATURAL.matcher( rawBuild ).matches() ) { thrownew InvalidBuildException(); } final Scanner scanner = newScanner( rawBuild ); finalint build = scanner.useDelimiter( PATTERN_BUILD ).nextInt(); scanner.close(); return build; } }

Scanner scanner = newScanner( newFile("poem.txt"), "UTF-8" ); String text = scanner.useDelimiter("\\A").next(); scanner.close();

private String convertStreamToString(java.io.InputStream is) { java.util.Scanner scanner = null; String result = ""; try { scanner = newjava.util.Scanner(is).useDelimiter("\\A"); result = scanner.hasNext() ? scanner.next() : ""; scanner.close(); } finally { if (scanner != null) scanner.close(); } return result; }

privatestatic String checkCgCompilerVersion(){ try { ProcessBuilder pb = new ProcessBuilder("cgc", "--version"); Process p = pb.start(); Scanner scan = newScanner(p.getErrorStream()); String ln = scan.nextLine(); scan.close(); p.waitFor(); String versionNumber = ln.split("\\s")[2]; return versionNumber.substring(0, versionNumber.length()-1); } catch (IOException ex) { logger.log(Level.SEVERE, "IOEx", ex); } catch (InterruptedException ex){ } return null; }

private String convertStreamToString(java.io.InputStream is) { java.util.Scanner scanner = null; String result=""; try { scanner = newjava.util.Scanner(is).useDelimiter("\\A"); result = scanner.hasNext() ? scanner.next() : ""; scanner.close(); } finally { if(scanner!=null) scanner.close(); } return result; }

publicvoid load(InputStream fis) throws IOException { Scanner in = newScanner(fis); ByteArrayOutputStream out = new ByteArrayOutputStream(); while (in.hasNext()) { out.write(in.nextLine().trim().getBytes()); out.write("\n".getBytes()); } in.close(); InputStream is = new ByteArrayInputStream(out.toByteArray()); super.load(is); } }

Sours: https://www.tabnine.com/code/java/methods/java.util.Scanner/close

Close a Scanner in Java

Close a in Java After Printing the Standard Input From the User
Close a in Java After Printing a Specified String That Has New Line Characters in Between
Use the Method to Close in Java After Reading the Contents of a File

In this tutorial, we will learn how to close a scanner in Java, and when we should use it. The class has a method that is especially available to close the opened scanner. Even if we don’t call the method explicitly, the interface will be invoked, closing the stream. It is a good practice to close a scanner explicitly.

Below are the examples that show how and when we can use the method.

Close a in Java After Printing the Standard Input From the User

In the code below, we have created a object that takes the standard input from the user in the constructor. The method returns the input that was skipped. It reads the entire line of input till the end of the line, including spaces and line separators.

The input is printed, and then we close the by calling the method on the object . After the is closed, if we want to use like we are doing below with , it will throw an exception because the stream or has been closed.

Output:

Close a in Java After Printing a Specified String That Has New Line Characters in Between

In this example, we will separate the string into different lines using and . is used to indicate a new line, and as the notices a new line, it goes to a new line and then prints it. Thus the output has all the three subjects in in different lines.

This is one of the situations when we might want to call the method as we don’t want the to scan any further new lines.

Output:

Use the Method to Close in Java After Reading the Contents of a File

It is recommended to always close the when we are reading a file. It ensures that no input or output stream is opened, which is not in use. The following example shows how we can read a string from the file and then close the once the operation has been done.

Output:

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Scanner close java

Scanner close() method in Java with Examples

Localized numbers

Number syntax

Java.util.Scanner.close() Method

Description

Declaration

Parameters

Return Value

Exception

Example

Close java scanner

Java Scanner close() Method

Syntax

Parameter

Returns

Exceptions

Compatibility Version

Example 1

Example 2

Example 3

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You will also like:

Close a Scanner in Java

Close a in Java After Printing the Standard Input From the User

Close a in Java After Printing a Specified String That Has New Line Characters in Between

Use the Method to Close in Java After Reading the Contents of a File

Related Article - Java Scanner