Package stdlib

Class In

java.lang.Object

stdlib.In

public final class In
extends Object

This class provides methods for reading strings and numbers from standard input, file input, URLs, and sockets.

The Locale used is: language = English, country = US. This is consistent with the formatting conventions with Java floating-point literals, command-line arguments (via Double.parseDouble(String)) and standard output.

For additional documentation, see Section 3.1 of Computer Science: An Interdisciplinary Approach by Robert Sedgewick and Kevin Wayne.

Like Scanner, reading a token also consumes preceding Java whitespace, reading a full line consumes the following end-of-line delimeter, while reading a character consumes nothing extra.

Whitespace is defined in Character.isWhitespace(char). Newlines consist of \n, \r, \r\n, and Unicode hex code points 0x2028, 0x2029, 0x0085; see Scanner.java (NB: Java 6u23 and earlier uses only \r, \r, \r\n).

Author:

David Pritchard, Robert Sedgewick, Kevin Wayne

Constructor Summary

Constructors

Constructor	Description
In()	Initializes an input stream from standard input.
In(String name)	Initializes an input stream from a filename or web page name.
In(Socket socket)	Initializes an input stream from a socket.
In(URL url)	Initializes an input stream from a URL.
In(Scanner scanner)	Initializes an input stream from a given Scanner source; use with new Scanner(String) to read from a string.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes this input stream.
boolean	exists()	Returns true if this input stream exists.
boolean	hasNextChar()	Returns true if this input stream has more input (including whitespace).
boolean	hasNextLine()	Returns true if this input stream has a next line.
boolean	isEmpty()	Returns true if input stream is empty (except possibly whitespace).
static void	main(String[] args)	Unit tests the In data type.
String	readAll()	Reads and returns the remainder of this input stream, as a string.
double[]	readAllDoubles()	Reads all remaining tokens from this input stream, parses them as doubles, and returns them as an array of doubles.
int[]	readAllInts()	Reads all remaining tokens from this input stream, parses them as integers, and returns them as an array of integers.
String[]	readAllLines()	Reads all remaining lines from this input stream and returns them as an array of strings.
long[]	readAllLongs()	Reads all remaining tokens from this input stream, parses them as longs, and returns them as an array of longs.
String[]	readAllStrings()	Reads all remaining tokens from this input stream and returns them as an array of strings.
boolean	readBoolean()	Reads the next token from this input stream, parses it as a boolean (interpreting either "true" or "1" as true, and either "false" or "0" as false).
byte	readByte()	Reads the next token from this input stream, parses it as a byte, and returns the byte.
char	readChar()	Reads and returns the next character in this input stream.
double	readDouble()	Reads the next token from this input stream, parses it as a double, and returns the double.
float	readFloat()	Reads the next token from this input stream, parses it as a float, and returns the float.
int	readInt()	Reads the next token from this input stream, parses it as a int, and returns the int.
String	readLine()	Reads and returns the next line in this input stream.
long	readLong()	Reads the next token from this input stream, parses it as a long, and returns the long.
short	readShort()	Reads the next token from this input stream, parses it as a short, and returns the short.
String	readString()	Reads the next token from this input stream and returns it as a String.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

In

public In()

Initializes an input stream from standard input.

In

public In(Socket socket)

Initializes an input stream from a socket.

Parameters:

socket - the socket

Throws:

IllegalArgumentException - if cannot open socket

IllegalArgumentException - if socket is null

In

public In(URL url)

Initializes an input stream from a URL.

Parameters:

url - the URL

Throws:

IllegalArgumentException - if cannot open url

IllegalArgumentException - if url is null

In

public In(String name)

Initializes an input stream from a filename or web page name.

Parameters:

name - the filename or web page name

Throws:

IllegalArgumentException - if cannot open name as a file or URL

IllegalArgumentException - if name is null

In

public In(Scanner scanner)

Initializes an input stream from a given Scanner source; use with new Scanner(String) to read from a string.

Note that this does not create a defensive copy, so the scanner will be mutated as you read on.

Parameters:

scanner - the scanner

Throws:

IllegalArgumentException - if scanner is null

Method Details

exists

public boolean exists()

Returns true if this input stream exists.

Returns:

true if this input stream exists; false otherwise

isEmpty

public boolean isEmpty()

Returns true if input stream is empty (except possibly whitespace). Use this to know whether the next call to readString(), readDouble(), etc will succeed.

Returns:

true if this input stream is empty (except possibly whitespace); false otherwise

hasNextLine

public boolean hasNextLine()

Returns true if this input stream has a next line. Use this method to know whether the next call to readLine() will succeed. This method is functionally equivalent to hasNextChar().

Returns:

true if this input stream has more input (including whitespace); false otherwise

hasNextChar

public boolean hasNextChar()

Returns true if this input stream has more input (including whitespace). Use this method to know whether the next call to readChar() will succeed. This method is functionally equivalent to hasNextLine().

Returns:

true if this input stream has more input (including whitespace); false otherwise

readLine

public String readLine()

Reads and returns the next line in this input stream.

Returns:

the next line in this input stream; null if no such line

readChar

public char readChar()

Reads and returns the next character in this input stream.

Returns:

the next char in this input stream

Throws:

NoSuchElementException - if the input stream is empty

readAll

public String readAll()

Reads and returns the remainder of this input stream, as a string.

Returns:

the remainder of this input stream, as a string

readString

public String readString()

Reads the next token from this input stream and returns it as a String.

Returns:

the next String in this input stream

Throws:

NoSuchElementException - if the input stream is empty

readInt

public int readInt()

Reads the next token from this input stream, parses it as a int, and returns the int.

Returns:

the next int in this input stream

Throws:

NoSuchElementException - if the input stream is empty

InputMismatchException - if the next token cannot be parsed as an int

readDouble

public double readDouble()

Reads the next token from this input stream, parses it as a double, and returns the double.

Returns:

the next double in this input stream

Throws:

NoSuchElementException - if the input stream is empty

InputMismatchException - if the next token cannot be parsed as a double

readFloat

public float readFloat()

Reads the next token from this input stream, parses it as a float, and returns the float.

Returns:

the next float in this input stream

Throws:

NoSuchElementException - if the input stream is empty

InputMismatchException - if the next token cannot be parsed as a float

readLong

public long readLong()

Reads the next token from this input stream, parses it as a long, and returns the long.

Returns:

the next long in this input stream

Throws:

NoSuchElementException - if the input stream is empty

InputMismatchException - if the next token cannot be parsed as a long

readShort

public short readShort()

Reads the next token from this input stream, parses it as a short, and returns the short.

Returns:

the next short in this input stream

Throws:

NoSuchElementException - if the input stream is empty

InputMismatchException - if the next token cannot be parsed as a short

readByte

public byte readByte()

Reads the next token from this input stream, parses it as a byte, and returns the byte.

To read binary data, use BinaryIn.

Returns:

the next byte in this input stream

Throws:

NoSuchElementException - if the input stream is empty

InputMismatchException - if the next token cannot be parsed as a byte

readBoolean

public boolean readBoolean()

Reads the next token from this input stream, parses it as a boolean (interpreting either "true" or "1" as true, and either "false" or "0" as false).

Returns:

the next boolean in this input stream

Throws:

NoSuchElementException - if the input stream is empty

InputMismatchException - if the next token cannot be parsed as a boolean

readAllStrings

public String[] readAllStrings()

Reads all remaining tokens from this input stream and returns them as an array of strings.

Returns:

all remaining tokens in this input stream, as an array of strings

readAllLines

public String[] readAllLines()

Reads all remaining lines from this input stream and returns them as an array of strings.

Returns:

all remaining lines in this input stream, as an array of strings

readAllInts

public int[] readAllInts()

Reads all remaining tokens from this input stream, parses them as integers, and returns them as an array of integers.

Returns:

all remaining lines in this input stream, as an array of integers

readAllLongs

public long[] readAllLongs()

Reads all remaining tokens from this input stream, parses them as longs, and returns them as an array of longs.

Returns:

all remaining lines in this input stream, as an array of longs

readAllDoubles

public double[] readAllDoubles()

Reads all remaining tokens from this input stream, parses them as doubles, and returns them as an array of doubles.

Returns:

all remaining lines in this input stream, as an array of doubles

close

public void close()

Closes this input stream.

main

public static void main(String[] args)

Unit tests the In data type.

Parameters:

args - the command-line arguments