Java : Scanner with Examples

final var sc = new Scanner(System.in);

while (sc.hasNext()) {

    final var next = sc.next();

    if ("quit".equals(next)) {
        System.out.println("Quit!");
        break;
    }

    System.out.println("next : " + next);
}

// Console
------------
Input
 ↓
abcd <Enter>

Output
 ↓
next : abcd

------------
Input
 ↓
123 XYZ <Enter>

Output
 ↓
next : 123
next : XYZ

------------
Input
 ↓
quit <Enter>

Output
 ↓
Quit!

Scanner (File source)

Constructs a new Scanner that produces values scanned from the specified file.

final var input = """
        abcd
        123
        """;
final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input);

try (final var sc = new Scanner(source.toFile())) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (File source, String charsetName)

Constructs a new Scanner that produces values scanned from the specified file.

final var input = """
        ○△×
        123
        """;
final var charsetName = "Shift_JIS";

final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input, Charset.forName(charsetName));

try (final var sc = new Scanner(source.toFile(), charsetName)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // ○△×

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (File source, Charset charset)

Constructs a new Scanner that produces values scanned from the specified file.

final var input = """
        ○△×
        123
        """;
final var charset = Charset.forName("Shift_JIS");

final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input, charset);

try (final var sc = new Scanner(source.toFile(), charset)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // ○△×

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (InputStream source)

Constructs a new Scanner that produces values scanned from the specified input stream.

final var input = """
        abcd
        123
        """;
final var source = new ByteArrayInputStream(input.getBytes());

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (InputStream source, String charsetName)

Constructs a new Scanner that produces values scanned from the specified input stream.

final var input = """
        ○△×
        123
        """;
final var charsetName = "Shift_JIS";
final var source = new ByteArrayInputStream(input.getBytes(charsetName));

try (final var sc = new Scanner(source, charsetName)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // ○△×

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (InputStream source, Charset charset)

Constructs a new Scanner that produces values scanned from the specified input stream.

final var input = """
        ○△×
        123
        """;
final var charset = Charset.forName("Shift_JIS");
final var source = new ByteArrayInputStream(input.getBytes(charset));

try (final var sc = new Scanner(source, charset)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // ○△×

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (Readable source)

Constructs a new Scanner that produces values scanned from the specified source.

final var input = """
        abcd
        123
        """;
final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input);

try (final var sc = new Scanner(Files.newBufferedReader(source))) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (String source)

Constructs a new Scanner that produces values scanned from the specified string.

final var source = """
        abcd
        123
        """;
try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (ReadableByteChannel source)

Constructs a new Scanner that produces values scanned from the specified channel.

final var input = """
        abcd
        123
        """;
final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input);

try (final var sc = new Scanner(
        Files.newByteChannel(source, StandardOpenOption.READ))) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (ReadableByteChannel source, String charsetName)

Constructs a new Scanner that produces values scanned from the specified channel.

final var input = """
        ○△×
        123
        """;
final var charsetName = "Shift_JIS";
final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input, Charset.forName(charsetName));

try (final var sc = new Scanner(
        Files.newByteChannel(source, StandardOpenOption.READ), charsetName)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // ○△×

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (ReadableByteChannel source, Charset charset)

Constructs a new Scanner that produces values scanned from the specified channel.

final var input = """
        ○△×
        123
        """;
final var charset = Charset.forName("Shift_JIS");
final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input, charset);

try (final var sc = new Scanner(
        Files.newByteChannel(source, StandardOpenOption.READ), charset)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // ○△×

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (Path source)

Constructs a new Scanner that produces values scanned from the specified file.

final var input = """
        abcd
        123
        """;
final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input);

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (Path source, String charsetName)

Constructs a new Scanner that produces values scanned from the specified file.

final var input = """
        ○△×
        123
        """;
final var charsetName = "Shift_JIS";

final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input, Charset.forName(charsetName));

try (final var sc = new Scanner(source, charsetName)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // ○△×

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner (Path source, Charset charset)

Constructs a new Scanner that produces values scanned from the specified file.

final var input = """
        ○△×
        123
        """;
final var charset = Charset.forName("Shift_JIS");

final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input, charset);

try (final var sc = new Scanner(source, charset)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // ○△×

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

void close ()

Closes this scanner.

final var input = """
        abcd
        123
        """;
final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input);

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

// An example without a try-with-resources statement.
final var input = """
        abcd
        123
        """;
final var source = Path.of("R:", "java-work", "aaa.txt");
System.out.println(source); // R:\java-work\aaa.txt

Files.writeString(source, input);

final var sc = new Scanner(source);
try {
    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123

} finally {
    sc.close();
}

Pattern delimiter ()

Returns the Pattern this Scanner is currently using to match delimiters.

final var source = """
        abcd XYZ
        123
        """;

try (final var sc = new Scanner(source)) {

    final var delimiter = sc.delimiter();
    System.out.println(delimiter); // \p{javaWhitespace}+

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // XYZ

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

final var source = "abcd=XYZ=123";

try (final var sc = new Scanner(source)) {

    sc.useDelimiter("=");

    final var delimiter = sc.delimiter();
    System.out.println(delimiter); // =

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // XYZ

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Stream<MatchResult> findAll (String patString)

Returns a stream of match results that match the provided pattern string.

This method is equivalent to findAll(Pattern.compile(patString)).

Stream<MatchResult> findAll (Pattern pattern)

Returns a stream of match results from this scanner.

final var source = "abcd 123 XYZ 456";

final var pattern = Pattern.compile("[a-zA-Z]+");
try (final var stream = new Scanner(source).findAll(pattern)) {

    final var ret = stream.map(MatchResult::group).toList();
    System.out.println(ret); // [abcd, XYZ]
}

final var source = "abcd 123 XYZ 456";

final var pattern = Pattern.compile("\\d+");
try (final var stream = new Scanner(source).findAll(pattern)) {

    final var ret = stream.map(MatchResult::group).toList();
    System.out.println(ret); // [123, 456]
}

String findInLine (String pattern)

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

This method is equivalent to findInLine(Pattern.compile(pattern)).

String findInLine (Pattern pattern)

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

final var source = """
        abcdefg
        123
        """;

try (final var sc = new Scanner(source)) {

    final var ret = sc.findInLine(Pattern.compile("cde"));
    System.out.println(ret); // cde

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // fg

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

final var source = """
        abcd
        123
        """;

try (final var sc = new Scanner(source)) {

    final var ret = sc.findInLine(Pattern.compile("XYZ"));
    System.out.println(ret); // null

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

String findWithinHorizon (String pattern, int horizon)

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

This method is equivalent to findWithinHorizon(Pattern.compile(pattern), horizon).

String findWithinHorizon (Pattern pattern, int horizon)

Attempts to find the next occurrence of the specified pattern.

final var source = """
        abcd
        XYZ
        """;

try (final var sc = new Scanner(source)) {

    final var ret = sc.findWithinHorizon(Pattern.compile("bc"), 2);
    System.out.println(ret); // null

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // XYZ
}

try (final var sc = new Scanner(source)) {

    final var ret = sc.findWithinHorizon(Pattern.compile("bc"), 3);
    System.out.println(ret); // bc

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // d

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // XYZ
}

boolean hasNext ()

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

final var source = """
        abcd efg
        XYZ
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // efg

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // XYZ

    System.out.println(sc.hasNext()); // false

    try {
        final var next = sc.next();
    } catch (NoSuchElementException e) {
        System.out.println("NoSuchElementException!");
    }

    // Result
    // ↓
    //NoSuchElementException!
}

boolean hasNext (String pattern)

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

This method is equivalent to hasNext(Pattern.compile(pattern)).

boolean hasNext (Pattern pattern)

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

final var source = "abcd XYZ";

try (final var sc = new Scanner(source)) {

    final var lower = Pattern.compile("[a-z]+");
    final var upper = Pattern.compile("[A-Z]+");

    System.out.println(sc.hasNext(lower)); // true
    System.out.println(sc.next(lower)); // abcd

    System.out.println(sc.hasNext(lower)); // false

    System.out.println(sc.hasNext(upper)); // true
    System.out.println(sc.next(upper)); // XYZ

    System.out.println(sc.hasNext(upper)); // false
}

boolean hasNextBigDecimal ()

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

final var source = """
        0.12345678901234567890123456789
        -9999.0
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextBigDecimal()); // true
    System.out.println(sc.nextBigDecimal()); // 0.12345678901234567890123456789

    System.out.println(sc.hasNextBigDecimal()); // true
    System.out.println(sc.nextBigDecimal()); // -9999.0

    System.out.println(sc.hasNextBigDecimal()); // false
}

boolean hasNextBigInteger ()

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

final var source = """
        123456789012345678901234567890
        -9999
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextBigInteger()); // true
    System.out.println(sc.nextBigInteger()); // 123456789012345678901234567890

    System.out.println(sc.hasNextBigInteger()); // true
    System.out.println(sc.nextBigInteger()); // -9999

    System.out.println(sc.hasNextBigInteger()); // false
}

boolean hasNextBigInteger (int radix)

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

Please see also : hasNextBigInteger()

final var source = """
        1234
        ff
        1000
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextBigInteger()); // true
    System.out.println(sc.nextBigInteger()); // 1234

    System.out.println(sc.hasNextBigInteger(16)); // true
    System.out.println(sc.nextBigInteger(16)); // 255

    System.out.println(sc.hasNextBigInteger(2)); // true
    System.out.println(sc.nextBigInteger(2)); // 8
}

boolean hasNextBoolean ()

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".

final var source = """
        true
        false
        TRUE
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextBoolean()); // true
    System.out.println(sc.nextBoolean()); // true

    System.out.println(sc.hasNextBoolean()); // true
    System.out.println(sc.nextBoolean()); // false

    System.out.println(sc.hasNextBoolean()); // true
    System.out.println(sc.nextBoolean()); // true

    System.out.println(sc.hasNextBoolean()); // false
}

boolean hasNextByte ()

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

This method is equivalent except a type to hasNextInt().

boolean hasNextByte (int radix)

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

This method is equivalent except a type to hasNextInt(int radix).

boolean hasNextDouble ()

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

final var source = """
        1.234
        9.99E-3
        -Infinity
        XYZ
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // 1.234

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // 0.00999

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // -Infinity

    System.out.println(sc.hasNextDouble()); // false

    try {
        final var next = sc.nextDouble();
    } catch (NoSuchElementException e) {
        System.out.println("NoSuchElementException!");
    }

    // Result
    // ↓
    //NoSuchElementException!
}

System.out.println(Double.MAX_VALUE); // 1.7976931348623157E308

final var source = """
        1.0E308
        1.0E309
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // 1.0E308

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // Infinity
}

boolean hasNextFloat ()

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

This method is equivalent except a type to hasNextDouble().

boolean hasNextInt ()

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

final var source = """
        1234
        -999
        XYZ
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 1234

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // -999

    System.out.println(sc.hasNextInt()); // false

    try {
        final var next = sc.nextInt();
    } catch (NoSuchElementException e) {
        System.out.println("NoSuchElementException!");
    }

    // Result
    // ↓
    //NoSuchElementException!
}

System.out.println(Integer.MAX_VALUE); // 2147483647

final var source = """
        2147483646
        2147483647
        2147483648
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 2147483646

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 2147483647

    System.out.println(sc.hasNextInt()); // false
}

boolean hasNextInt (int radix)

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

Please see also : hasNextInt()

final var source = """
        1234
        ff
        1000
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 1234

    System.out.println(sc.hasNextInt(16)); // true
    System.out.println(sc.nextInt(16)); // 255

    System.out.println(sc.hasNextInt(2)); // true
    System.out.println(sc.nextInt(2)); // 8
}

boolean hasNextLine ()

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

final var source = """
        abcd efg
        XYZ
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextLine()); // true
    System.out.println(sc.nextLine()); // abcd efg

    System.out.println(sc.hasNextLine()); // true
    System.out.println(sc.nextLine()); // XYZ

    System.out.println(sc.hasNextLine()); // false

    try {
        final var next = sc.nextLine();
    } catch (NoSuchElementException e) {
        System.out.println("NoSuchElementException!");
    }

    // Result
    // ↓
    //NoSuchElementException!
}

boolean hasNextLong ()

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

This method is equivalent except a type to hasNextInt().

boolean hasNextLong (int radix)

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

This method is equivalent except a type to hasNextInt(int radix).

boolean hasNextShort ()

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

This method is equivalent except a type to hasNextInt().

boolean hasNextShort (int radix)

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

This method is equivalent except a type to hasNextInt(int radix).

IOException ioException ()

Returns the IOException last thrown by this Scanner's underlying Readable.

try (final var sc = new Scanner("abcd")) {

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    final var ret = sc.ioException();
    System.out.println(ret); // null
}

final var source = new StringReader("abcd");
try (final var sc = new Scanner(source)) {

    // Intentionally close the source object to make an error.
    source.close();
    System.out.println(sc.hasNext()); // false

    final var ret = sc.ioException();
    System.out.println(ret); // java.io.IOException: Stream closed
}

Locale locale ()

Returns this scanner's locale.

System.out.println(Locale.getDefault(Locale.Category.FORMAT)); // en_US

try (final var sc = new Scanner("abcd")) {

    System.out.println(sc.locale()); // en_US

    sc.useLocale(Locale.JAPAN);
    System.out.println(sc.locale()); // ja_JP
}

MatchResult match ()

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

try (final var sc = new Scanner("abcdefg")) {

    System.out.println(sc.findInLine(Pattern.compile("cde"))); // cde

    final var ret = sc.match();
    System.out.println(ret.group()); // cde
    System.out.println(ret.start()); // 2
    System.out.println(ret.end()); // 5
}

String next ()

Finds and returns the next complete token from this scanner.

Please see hasNext().

String next (String pattern)

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

This method is equivalent to next(Pattern.compile(pattern)).

String next (Pattern pattern)

Returns the next token if it matches the specified pattern.

final var source = "abcd XYZ";

try (final var sc = new Scanner(source)) {

    final var lower = Pattern.compile("[a-z]+");
    final var upper = Pattern.compile("[A-Z]+");

    System.out.println(sc.hasNext(lower)); // true
    System.out.println(sc.next(lower)); // abcd

    System.out.println(sc.hasNext(lower)); // false

    System.out.println(sc.hasNext(upper)); // true
    System.out.println(sc.next(upper)); // XYZ

    System.out.println(sc.hasNext(upper)); // false
}

BigDecimal nextBigDecimal ()

Scans the next token of the input as a BigDecimal.

Please see hasNextBigDecimal().

BigInteger nextBigInteger ()

Scans the next token of the input as a BigInteger.

Please see hasNextBigInteger().

BigInteger nextBigInteger (int radix)

Scans the next token of the input as a BigInteger.

Please see hasNextBigInteger(int radix).

boolean nextBoolean ()

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

Please see hasNextBoolean().

byte nextByte ()

Scans the next token of the input as a byte.

This method is equivalent except a type to nextInt().

byte nextByte (int radix)

Scans the next token of the input as a byte.

This method is equivalent except a type to nextInt(int radix).

double nextDouble ()

Scans the next token of the input as a double.

final var source = """
        1.234
        9.99E-3
        -Infinity
        XYZ
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // 1.234

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // 0.00999

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // -Infinity

    System.out.println(sc.hasNextDouble()); // false

    try {
        final var next = sc.nextDouble();
    } catch (NoSuchElementException e) {
        System.out.println("NoSuchElementException!");
    }

    // Result
    // ↓
    //NoSuchElementException!
}

System.out.println(Double.MAX_VALUE); // 1.7976931348623157E308

final var source = """
        1.0E308
        1.0E309
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // 1.0E308

    System.out.println(sc.hasNextDouble()); // true
    System.out.println(sc.nextDouble()); // Infinity
}

float nextFloat ()

Scans the next token of the input as a float.

This method is equivalent except a type to nextDouble().

int nextInt ()

Scans the next token of the input as an int.

final var source = """
        1234
        -999
        XYZ
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 1234

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // -999

    System.out.println(sc.hasNextInt()); // false

    try {
        final var next = sc.nextInt();
    } catch (NoSuchElementException e) {
        System.out.println("NoSuchElementException!");
    }

    // Result
    // ↓
    //NoSuchElementException!
}

System.out.println(Integer.MAX_VALUE); // 2147483647

final var source = """
        2147483646
        2147483647
        2147483648
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 2147483646

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 2147483647

    System.out.println(sc.hasNextInt()); // false
}

int nextInt (int radix)

Scans the next token of the input as an int.

Please see also : nextInt()

final var source = """
        1234
        ff
        1000
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 1234

    System.out.println(sc.hasNextInt(16)); // true
    System.out.println(sc.nextInt(16)); // 255

    System.out.println(sc.hasNextInt(2)); // true
    System.out.println(sc.nextInt(2)); // 8
}

String nextLine ()

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

Please see hasNextLine().

long nextLong ()

Scans the next token of the input as a long.

This method is equivalent except a type to nextInt().

long nextLong (int radix)

Scans the next token of the input as a long.

This method is equivalent except a type to nextInt(int radix).

short nextShort ()

Scans the next token of the input as a short.

This method is equivalent except a type to nextInt().

short nextShort (int radix)

Scans the next token of the input as a short.

This method is equivalent except a type to nextInt(int radix).

int radix ()

Returns this scanner's default radix.

final var source = """
        1234
        ff
        """;

try (final var sc = new Scanner(source)) {

    System.out.println(sc.radix()); // 10

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 1234

    System.out.println(sc.hasNextInt()); // false

    sc.useRadix(16);
    System.out.println(sc.radix()); // 16

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 255
}

void remove ()

The remove operation is not supported by this implementation of Iterator.

try (final var sc = new Scanner("abcd")) {

    try {
        sc.remove();
    } catch (UnsupportedOperationException e) {
        System.out.println("UnsupportedOperationException!");
    }

    // Result
    // ↓
    //UnsupportedOperationException!
}

Scanner reset ()

Resets this scanner.

try (final var sc = new Scanner("abcd")) {

    System.out.println(sc.delimiter()); // \p{javaWhitespace}+
    System.out.println(sc.locale()); // en_US
    System.out.println(sc.radix()); // 10

    sc.useDelimiter("=").useLocale(Locale.JAPAN).useRadix(16);

    System.out.println(sc.delimiter()); // =
    System.out.println(sc.locale()); // ja_JP
    System.out.println(sc.radix()); // 16

    sc.reset();

    System.out.println(sc.delimiter()); // \p{javaWhitespace}+
    System.out.println(sc.locale()); // en_US
    System.out.println(sc.radix()); // 10
}

Scanner skip (String pattern)

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

This method is equivalent to skip(Pattern.compile(pattern)).

Scanner skip (Pattern pattern)

Skips input that matches the specified pattern, ignoring delimiters.

final var source = "abcd 123 XYZ 456";

final var pattern = Pattern.compile("\\p{javaWhitespace}*\\p{Alpha}+");
try (final var sc = new Scanner(source)) {

    System.out.println(sc.hasNextInt()); // false

    sc.skip(pattern);

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123

    System.out.println(sc.hasNextInt()); // false

    sc.skip(pattern);

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.next()); // 456
}

Stream<String> tokens ()

Returns a stream of delimiter-separated tokens from this scanner.

final var source = """
        abcd XYZ
        123
        """;

try (final var stream = new Scanner(source).tokens()) {

    System.out.println(stream.toList()); // [abcd, XYZ, 123]
}

String toString ()

Returns the string representation of this Scanner.

try (final var sc = new Scanner("abcd")) {

    final var str = sc.toString();
    System.out.println(str);
}

// Result
// ↓
//java.util.Scanner[delimiters=\p{javaWhitespace}+][position=0][match valid=false]
// [need input=false][source closed=false][skipped=false][group separator=\x{2c}]
// [decimal separator=\x{2e}][positive prefix=][negative prefix=\Q-\E]
// [positive suffix=][negative suffix=][NaN string=\QNaN\E][infinity string=\Q∞\E]

Scanner useDelimiter (String pattern)

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

Please see delimiter().

Scanner useDelimiter (Pattern pattern)

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

final var source = "abcd=XYZ=123";

try (final var sc = new Scanner(source)) {

    sc.useDelimiter(Pattern.compile("="));

    final var delimiter = sc.delimiter();
    System.out.println(delimiter); // =

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // abcd

    System.out.println(sc.hasNext()); // true
    System.out.println(sc.next()); // XYZ

    System.out.println(sc.hasNextInt()); // true
    System.out.println(sc.nextInt()); // 123
}

Scanner useLocale (Locale locale)

Sets this scanner's locale to the specified locale.

Please see locale().

Scanner useRadix (int radix)

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

Please see radix().

forEachRemaining

Please see the link below.

• Java API Examples : Iterator