EasyReader

java.lang.Object
- java.io.Reader
- - java.io.FilterReader
  - - java.io.PushbackReader
    - - edu.colorado.io.EasyReader

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, java.lang.Readable
```
public class EasyReader
extends java.io.PushbackReader
```
The EasyReader object has a small collection of methods for reading some primitive data values from an input stream or file.
Limitations:
If an IOException or FileNotFoundException occurs during any operation, then the EasyReader prints an error message and halts the program. The exceptions is not passed back to the calling program, so the calling program does not need to catch any exceptions.
Example:
This example declares an EasyReader that is attached to the keyboard input (System.in). It then uses doubleQuery to ask the user to enter a double number. The square of this double number is then printed: import edu.colorado.io.EasyReader ... EasyReader stdin = new EasyReader(System.in); // Attaches to keyboard double d; d = stdin.doubleQuery("Please type a double value: "); System.out.println("The square of that is: " + d*d); The EasyReader class includes: (1) Three constructors to create an EasyReader from an InputStream, from an InputStreamReader, or from a file name. For example, to create an EasyReader from System.in:
EasyReader stdin = new EasyReader(System.in); (2) Query methods: The names of these methods end with "Query". Each method prints a prompt (which is a String parameter) and then reads one line of input, converting the line to some type (char, double, int, or String). All of the query methods reject improperly formatted input lines (such as a 1.5 for an integer input). When an input line is rejected, the method prompts the user for a correctly formatted input. This continues until an input line is typed in the correct format. (3) Peek method: This method returns the next character of the input without actually reading it. (4) Input methods: The names of these methods end with "Input" or "InputLine". The methods read input and convert it to some type (char, double, int, or String). The "Input" methods just read the data, and the "InputLine" methods read the data and then discard the rest of the line. (5) Boolean methods: The names of these methods begin with "is". They return various information about the input status. (6) The methods skipLine and ignore. They read and throw away various input. Java Source Code for this class: http://www.cs.colorado.edu/~main/edu/colorado/io/EasyReader.java

See Also:

FormatWriter

Constructor Summary

Constructors
Constructor and Description
`EasyReader(java.io.InputStream in)` Initialize this `EasyReader` so that it reads from an `InputStream`.
`EasyReader(java.io.InputStreamReader isr)` Initialize this `EasyReader` so that it reads from an `InputStreamReader`.
`EasyReader(java.lang.String name)` Initialize this `EasyReader` so that it reads from a specified file.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`char`	`charInput()` Read a character from this `EasyReader`.
`char`	`charInputLine()` Read a character from a complete line of this `EasyReader`.
`char`	`charQuery(java.lang.String prompt)` Print a prompt, then read and return a character from this `EasyReader`.
`double`	`doubleInput()` Read a `double` number from this `EasyReader`.
`double`	`doubleInputLine()` Read a double value from a complete line of this `EasyReader`.
`double`	`doubleQuery(java.lang.String prompt)` Print a prompt, then read and return a double value from this `EasyReader`.
`void`	`ignore()` Read and discard one character.
`int`	`intInput()` Read an integer from this `EasyReader`.
`int`	`intInputLine()` Read an integer from a complete line of this `EasyReader`.
`int`	`intQuery(java.lang.String prompt)` Print a prompt, then read and return an integer from this `EasyReader`.
`boolean`	`isEOF()` Determine whether this `EasyReader` has reached the end-of-file.
`boolean`	`isEOLN()` Determine whether the next input character is an end-of-line.
`boolean`	`isFormatProblem()` Determine whether there was an incorrectly formatted input to the most recent input operation.
`static void`	`main(java.lang.String[] args)` A demonstration program.
`static void`	`pause(long milliseconds)` Make the computation pause for a specified number of milliseconds.
`char`	`peek()` Peek ahead at the next character from this `EasyReader` (but don't read it).
`boolean`	`query(java.lang.String prompt)` Print a prompt, then read and return a YES/NO answer from this `EasyReader`.
`void`	`skipLine()` Read and discard the rest of the current input line.
`java.lang.String`	`stringInput()` Read a `String` (up to whitespace) from this `EasyReader`.
`java.lang.String`	`stringInputLine()` Read a `String` from a complete line of this `EasyReader`.
`java.lang.String`	`stringQuery(java.lang.String prompt)` Print a prompt, then read and return a `String` from this `EasyReader`.

Methods inherited from class java.io.PushbackReader
close, mark, markSupported, read, read, ready, reset, skip, unread, unread, unread

Methods inherited from class java.io.Reader
read, read

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - EasyReader
```
public EasyReader(java.io.InputStream in)
```
    Initialize this EasyReader so that it reads from an InputStream.
    
    Parameters:
    
    in - an InputStream that this EasyReader will read from Postcondition: This EasyReader has been initialized so that its subsequent input comes from the specified InputStream. Example: EasyReader stdin = new EasyReader(System.in);
  - EasyReader
```
public EasyReader(java.lang.String name)
```
    Initialize this EasyReader so that it reads from a specified file.
    
    Parameters:
    
    name - the name of the file that this EasyReader will read from Postcondition: This EasyReader has been initialized so that its subsequent input comes from the specified file. If the file does not exist, then an error message is printed to System.err and the program exits. Example: EasyReader stdin = new EasyReader("foo.txt");
  - EasyReader
```
public EasyReader(java.io.InputStreamReader isr)
```
    Initialize this EasyReader so that it reads from an InputStreamReader.
    
    Parameters:
    
    isr - an InputStreamReader that this EasyReader will read from Postcondition: This EasyReader has been initialized so that its subsequent input comes from the specified InputStreamReader.
- Method Detail
  - charInput
```
public char charInput()
```
    Read a character from this EasyReader.
    
    Returns:
    
    a character that's been read Note: This method reads and throws away whitespace. Then it reads and returns the next character. If end-of-file has been reached, then it returns ASCII value zero.
  - charInputLine
```
public char charInputLine()
```
    Read a character from a complete line of this EasyReader.
    
    Returns:
    
    a character that's been read Note: This method is indentical charInput() with an added activation of skipLine() just before returning.
  - charQuery
```
public char charQuery(java.lang.String prompt)
```
    Print a prompt, then read and return a character from this EasyReader.
    
    Parameters:
    
    prompt - a prompt to print
    
    Returns:
    
    The prompt has been printed to System.out. Then a character has been read and returned with charInputLine.
  - doubleInput
```
public double doubleInput()
```
    Read a double number from this EasyReader.
    
    Returns:
    
    a double number that's been read Input Method: An attempt is made to read the following items into a String: (1) Zero or more whitespace characters (which are discarded); (2) An optional + or - sign. (3) A sequence of digits that form the integer part of the number. (4) If the next character is a decimal point, then it is read along with a sequence of digits that form the fractional part of the number. (5) If the next character is 'e' or 'E', then it is read along with an optional +/- sign and digits that form the exponent part of the number. After these items, there may be a non-digit delimiter, or the end-of-file may appear after the number. The delimiter (or EOF) is not read. Conversion: The above items are converted to a double value using Double.valueOf. Format Problems: If a NumberFormatException occurs, then the method returns Double.NaN and an immediate activation of isFormatProblem() will return true.
  - doubleInputLine
```
public double doubleInputLine()
```
    Read a double value from a complete line of this EasyReader.
    
    Returns:
    
    a double value that's been read Note: This method is identical doubleInput( ) with an added activation of skipLine( ) just before returning.
  - doubleQuery
```
public double doubleQuery(java.lang.String prompt)
```
    Print a prompt, then read and return a double value from this EasyReader.
    
    Parameters:
    
    prompt - a prompt to print
    
    Returns:
    
    The prompt has been printed to System.out. Then a double value has been read and returned with doubleInputLine. Format Problems: If doubleInputLine encounters a format problem, but !isEOF(), then the user is prompted to type a new input line until a correct double value is provided. If end-of-file is reached, then the method returns Double.NaN and an immediate activation of isFormatProblem() will return true.
  - ignore
```
public void ignore()
```
    Read and discard one character. Postcondition: One character has been read and discarded.
  - intInput
```
public int intInput()
```
    Read an integer from this EasyReader.
    
    Returns:
    
    an integer that's been read Format: An attempt is made to read the following items into a String: (1) Zero or more whitespace characters (which are discarded); (2) An optional + or - sign. (3) A sequence of digits that form the actual integer. There may be a non-digit delimiter after the integer, or the end-of-file may appear after the integer. The delimiter (or EOF) is not read. Conversion: The above items are converted to an integer value using Integer.parseInt. Format Problems: If a NumberFormatException occurs, then the method returns Integer.MIN_VALUE and an immediate activation of isFormatProblem() will return true.
  - intInputLine
```
public int intInputLine()
```
    Read an integer from a complete line of this EasyReader.
    
    Returns:
    
    an integer that's been read Note: This method is indentical intInput( ) with an added activation of skipLine( ) just before returning.
  - intQuery
```
public int intQuery(java.lang.String prompt)
```
    Print a prompt, then read and return an integer from this EasyReader.
    
    Parameters:
    
    prompt - a prompt to print
    
    Returns:
    
    The prompt has been printed to System.out. Then an integer has been read and returned with intInputLine. Format Problems: If intInputLine encounters a format problem, but !isEOF(), then the user is prompted to type a new input line until a correct int value is provided. If end-of-file is reached, then the method returns Integer.MIN_VALUE and an immediate activation of isFormatProblem() will return true.
  - isEOF
```
public boolean isEOF()
```
    Determine whether this EasyReader has reached the end-of-file.
    
    Returns:
    
    If this EasyReader has reached the end of file (reading all characters up to but not including EOF), then the return value is true; if an attempt to read causes an IOException, then the return value is also true; otherwise the return value is false. Note: A user at the keyboard indicates EOF for standard input by typing ctrl-z (MS Windows) or ctrl-c (Unix). For an interactive user, this method does pause until the user provides some input or indicates end-of-file by pressing ctrl-z. Example: Read one integer per line from standard input until EOF, then print the sum of all the integers: EasyReader stdin = new EasyReader(System.in); int sum = 0; System.out.println("Type one int per line and press ctrl-z to end:"); while (!stdin.isEOF( )) sum += stdin.intInputLine( ); System.out.println("Total sum: " + sum);
  - isEOLN
```
public boolean isEOLN()
```
    Determine whether the next input character is an end-of-line.
    
    Returns:
    
    If the next input character is a newline ('\n') or carriage return ('\r'), then the return value is true; if isEOF(), then the return value is also true; if an attempt to read causes an IOException, then the return value is also true; otherwise the return value is false.
  - isFormatProblem
```
public boolean isFormatProblem()
```
    Determine whether there was an incorrectly formatted input to the most recent input operation.
    
    Returns:
    
    A true return value indicates that the most recent activation of an input methods had an IOException OR was given input of the wrong form (such as "abc" instead of an integer). Note that the return value is applicable to only the MOST RECENT activation of these input methods: doubleInput, intInput doubleInputLine, intInputLine doubleQuery, intQuery
  - pause
```
public static void pause(long milliseconds)
```
    Make the computation pause for a specified number of milliseconds.
    
    Parameters:
    
    milliseconds - the number of milliseconds to pause Postcondition: The computation has paused for the specified time.
  - peek
```
public char peek()
```
    Peek ahead at the next character from this EasyReader (but don't read it).
    
    Returns:
    
    The return value is the next character that will be read from this EasyReader. If there is no next character (because of the end-of-file marker), then the return value is '\0'.
  - query
```
public boolean query(java.lang.String prompt)
```
    Print a prompt, then read and return a YES/NO answer from this EasyReader.
    
    Parameters:
    
    prompt - a prompt to print
    
    Returns:
    
    stringQuery(prompt) has been called to ask a question and read the answer, which is considered true if it begins with "Y" or "y" and false if it begins with "N" or "n". If the answer did not begin with a lower- or upper-case Y or N, then the process is repeated until a correct Yes/No answer is provided. If EOF is reached, then false is returned.
  - skipLine
```
public void skipLine()
```
    Read and discard the rest of the current input line. Postcondition: Characters have been read and discarded up to and including the end of the current input line (or to the end-of-file).
  - stringInput
```
public java.lang.String stringInput()
```
    Read a String (up to whitespace) from this EasyReader.
    
    Returns:
    
    a String that's been read Format: Whitespace has been skipped, and then a string has been read up to but not including the next whitespace character.
  - stringInputLine
```
public java.lang.String stringInputLine()
```
    Read a String from a complete line of this EasyReader.
    
    Returns:
    
    a String that's been read Format: An entire line of characters has been read up to and including the end of the current line (or the end-of-file). All characters before the end are returned in a String.
  - stringQuery
```
public java.lang.String stringQuery(java.lang.String prompt)
```
    Print a prompt, then read and return a String from this EasyReader.
    
    Parameters:
    
    prompt - a prompt to print
    
    Returns:
    
    The prompt has been printed to System.out. Then a String has been read and returned with stringInputLine.
  - main
```
public static void main(java.lang.String[] args)
```
    A demonstration program. To run the demonstration:
    java edu.colorado.io.EasyReader
    
    Parameters:
    
    args - not used in this implementation

Class EasyReader

Constructor Summary

Method Summary

Methods inherited from class java.io.PushbackReader

Methods inherited from class java.io.Reader

Methods inherited from class java.lang.Object

Constructor Detail

EasyReader

EasyReader

EasyReader

Method Detail

charInput

charInputLine

charQuery

doubleInput

doubleInputLine

doubleQuery

ignore

intInput

intInputLine

intQuery

isEOF

isEOLN

isFormatProblem

pause

peek

query

skipLine

stringInput

stringInputLine

stringQuery

main