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<MatchResult> | 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<String> | 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: tutor aspire Name is: tutor aspire
Example 2
Output:
Boolean Result: true String: Hello, This is tutoraspire. -------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 tutoraspire My name is Abhishek. Delimiter used: /