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Java Scanner

Scanner class in Java is found in the java.util package. Java provides various ways to read input from the keyboard, the java.util.Scanner class is one of them.

The Java Scanner class breaks the input into tokens using a delimiter which is whitespace by default. It provides many methods to read and parse various primitive values.

The Java Scanner class is widely used to parse text for strings and primitive types using a regular expression. It is the simplest way to get input in Java. By the help of Scanner in Java, we can get input from the user in primitive types such as int, long, double, byte, float, short, etc.

The Java Scanner class extends Object class and implements Iterator and Closeable interfaces.

The Java Scanner class provides nextXXX() methods to return the type of value such as nextInt(), nextByte(), nextShort(), next(), nextLine(), nextDouble(), nextFloat(), nextBoolean(), etc. To get a single character from the scanner, you can call next().charAt(0) method which returns a single character.

Java Scanner Class Declaration

How to get Java Scanner

To get the instance of Java Scanner which reads input from the user, we need to pass the input stream (System.in) in the constructor of Scanner class. For Example:

To get the instance of Java Scanner which parses the strings, we need to pass the strings in the constructor of Scanner class. For Example:

Java Scanner Class Constructors

SN Constructor Description
1) Scanner(File source) It constructs a new Scanner that produces values scanned from the specified file.
2) Scanner(File source, String charsetName) It constructs a new Scanner that produces values scanned from the specified file.
3) Scanner(InputStream source) It constructs a new Scanner that produces values scanned from the specified input stream.
4) Scanner(InputStream source, String charsetName) It constructs a new Scanner that produces values scanned from the specified input stream.
5) Scanner(Readable source) It constructs a new Scanner that produces values scanned from the specified source.
6) Scanner(String source) It constructs a new Scanner that produces values scanned from the specified string.
7) Scanner(ReadableByteChannel source) It constructs a new Scanner that produces values scanned from the specified channel.
8) Scanner(ReadableByteChannel source, String charsetName) It constructs a new Scanner that produces values scanned from the specified channel.
9) Scanner(Path source) It constructs a new Scanner that produces values scanned from the specified file.
10) Scanner(Path source, String charsetName) It constructs a new Scanner that produces values scanned from the specified file.

Java Scanner Class Methods

The following are the list of Scanner methods:

SN Modifier & Type Method Description
1) void close() It is used to close this scanner.
2) pattern delimiter() It is used to get the Pattern which the Scanner class is currently using to match delimiters.
3) Stream findAll() It is used to find a stream of match results that match the provided pattern string.
4) String findInLine() It is used to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.
5) string findWithinHorizon() It is used to find the next occurrence of a pattern constructed from the specified string, ignoring delimiters.
6) boolean hasNext() It returns true if this scanner has another token in its input.
7) boolean hasNextBigDecimal() It is used to check if the next token in this scanner's input can be interpreted as a BigDecimal using the nextBigDecimal() method or not.
8) boolean hasNextBigInteger() It is used to check if the next token in this scanner's input can be interpreted as a BigDecimal using the nextBigDecimal() method or not.
9) boolean hasNextBoolean() It is used to check if the next token in this scanner's input can be interpreted as a Boolean using the nextBoolean() method or not.
10) boolean hasNextByte() It is used to check if the next token in this scanner's input can be interpreted as a Byte using the nextBigDecimal() method or not.
11) boolean hasNextDouble() It is used to check if the next token in this scanner's input can be interpreted as a BigDecimal using the nextByte() method or not.
12) boolean hasNextFloat() It is used to check if the next token in this scanner's input can be interpreted as a Float using the nextFloat() method or not.
13) boolean hasNextInt() It is used to check if the next token in this scanner's input can be interpreted as an int using the nextInt() method or not.
14) boolean hasNextLine() It is used to check if there is another line in the input of this scanner or not.
15) boolean hasNextLong() It is used to check if the next token in this scanner's input can be interpreted as a Long using the nextLong() method or not.
16) boolean hasNextShort() It is used to check if the next token in this scanner's input can be interpreted as a Short using the nextShort() method or not.
17) IOException ioException() It is used to get the IOException last thrown by this Scanner's readable.
18) Locale locale() It is used to get a Locale of the Scanner class.
19) MatchResult match() It is used to get the match result of the last scanning operation performed by this scanner.
20) String next() It is used to get the next complete token from the scanner which is in use.
21) BigDecimal nextBigDecimal() It scans the next token of the input as a BigDecimal.
22) BigInteger nextBigInteger() It scans the next token of the input as a BigInteger.
23) boolean nextBoolean() It scans the next token of the input into a boolean value and returns that value.
24) byte nextByte() It scans the next token of the input as a byte.
25) double nextDouble() It scans the next token of the input as a double.
26) float nextFloat() It scans the next token of the input as a float.
27) int nextInt() It scans the next token of the input as an Int.
28) String nextLine() It is used to get the input string that was skipped of the Scanner object.
29) long nextLong() It scans the next token of the input as a long.
30) short nextShort() It scans the next token of the input as a short.
31) int radix() It is used to get the default radix of the Scanner use.
32) void remove() It is used when remove operation is not supported by this implementation of Iterator.
33) Scanner reset() It is used to reset the Scanner which is in use.
34) Scanner skip() It skips input that matches the specified pattern, ignoring delimiters
35) Stream tokens() It is used to get a stream of delimiter-separated tokens from the Scanner object which is in use.
36) String toString() It is used to get the string representation of Scanner using.
37) Scanner useDelimiter() It is used to set the delimiting pattern of the Scanner which is in use to the specified pattern.
38) Scanner useLocale() It is used to sets this scanner's locale object to the specified locale.
39) Scanner useRadix() It is used to set the default radix of the Scanner which is in use to the specified radix.

Example 1

Let's see a simple example of Java Scanner where we are getting a single input from the user. Here, we are asking for a string through in.nextLine() method.

Output:

Enter your name: sonoo jaiswal
Name is: sonoo jaiswal

Example 2

Output:

Boolean Result: true
String: Hello, This is JavaTpoint.
-------Enter Your Details--------- 
Enter your name: Abhishek
Name: Abhishek
Enter your age: 23
Age: 23
Enter your salary: 25000
Salary: 25000.0

Example 3

Output:

Boolean Result: false
---Tokenizes String---
Hello
This is JavaTpoint
My name is Abhishek.
Delimiter used: /
Next TopicPrintStream class




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