Object
- edu.princeton.cs.algs4.In

```
public final class In
extends Object
```
The In data type 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 delimiter, 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(File file)`	Initializes an input stream from a file.
`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

All Methods Static Methods Instance Methods Concrete Methods
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, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - 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(File file)
```
    Initializes an input stream from a file.
    
    Parameters:
    
    file - the file
    
    Throws:
    
    IllegalArgumentException - if cannot open file
    
    IllegalArgumentException - if file 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 Detail
  - 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

Class In

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

In

In

In

In

In

In

Method Detail

exists

isEmpty

hasNextLine

hasNextChar

readLine

readChar

readAll

readString

readInt

readDouble

readFloat

readLong

readShort

readByte

readBoolean

readAllStrings

readAllLines

readAllInts

readAllLongs

readAllDoubles

close

main