Homepage : Rhul

java.lang.Object
- uk.ac.rhul.cs.oo.Rhul

```
public final class Rhul
extends java.lang.Object
```
The Rhul class features:
- I/O operations,
- drawings,
- some string operations.
The Rhul class masks some more advanced Java constructs that are not relevant in the context of a first programming course. These advanced features will be uncovered in due time. The names in the Rhul class have been chosen uniformly to ease programming.
Input/Outputs (I/O)

The inputs are always from the keyboard and the outputs are always shown in the terminal.

The methods print(type) and println(type) allow to print any data type (println adds a newline at the end).

The input methods are of the form readType() for all the Java primitives data types. In case of an error, all these methods will update a flag that can be accessed using the isOk() and getStatus().

Drawings

An example of graphical program is the following:
```
 Rhul.startDrawings(200,200);
 for (i=0; i < 200; i+=4) {
   Rhul.setGray(i);
   Rhul.drawLine(0,i,199,199-i);
   Rhul.drawLine(i,0,199-i,199);
 }
 Rhul.stopDrawings();
 
```
It produces:

String operations
The provided methods are of the form typeToString() and stringTotype() where (type can be: boolean, int, long, float ou double). These methods provide the expected conversions from and to String.
The following comparison methods are also included: equals(), compare(), subString(), charAt() et length().

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`ARG_ERROR` The arguments is invalid (ex: `==null`).
`static int`	`FORMAT_ERROR` The conversion of the character string that was read to the needed data type was not possible.
`static int`	`NO_ERROR` The last I/O operation went well.
`static int`	`STREAM_ERROR` Reading the input stream was impossible.

Method Summary

Methods
Modifier and Type	Method and Description
`static java.lang.String`	`booleanToString(boolean value)` Converts a boolean to a character string (`String`).
`static char`	`charAt(java.lang.String aString, int position)` Extracts the character at a given position in a character string.
`static java.lang.String`	`charToString(char value)` Converts a character to a character string (`String`).
`static void`	`clearArea()` Clears the diplay area completely.
`static int`	`compare(java.lang.String aString, java.lang.String anotherString)` Compares two character strings.
`static java.lang.String`	`doubleToString(double value)` Converts a double-precision floating point number to a character string (`String`).
`static void`	`drawArc(int x, int y, int r, int angleInit, int angleCouvert)` Draws an arc in the display zone.
`static void`	`drawCircle(int x, int y, int r)` Draws a circle in the display zone.
`static void`	`drawLine(int x0, int y0, int x1, int y1)` Draws a line between two points in the drawing area.
`static void`	`drawPoint(int x, int y)` Draws a point in the drawing zone.
`static void`	`drawRect(int x, int y, int w, int h)` Draws an empty rectangle in the display zone.
`static boolean`	`equals(java.lang.String aString, java.lang.String anotherString)` Tests the equality between two character strings.
`static void`	`exit()` Terminates the program.
`static void`	`fillArc(int x, int y, int r, int angleInit, int angleCouvert)` Draws an filled arc in the display zone.
`static void`	`fillCircle(int x, int y, int r)` Draws a filled circle in the display zone.
`static void`	`fillRect(int x, int y, int w, int h)` Draws a filled rectangle in the display zone.
`static java.lang.String`	`floatToString(float value)` Converts a single-precision floating point number to a character string (`String`).
`static int`	`getStatus()` Returns the error code of the last I/O operation.
`static java.lang.String`	`intToString(int value)` Converts an integer to a character string (`String`).
`static boolean`	`isOk()` This method return the error state of the last I/o operation.
`static int`	`length(java.lang.String aString)` Computes the length of a given character string.
`static java.lang.String`	`longToString(long value)` Converts a long integer to a character string (`String`).
`static void`	`print(boolean b)` Prints a boolean (`boolean`)
`static void`	`print(char c)` Prints a character.
`static void`	`print(double d)` Prints a double-precision flooating point number (`double`)
`static void`	`print(float f)` Prints a single-precision floating point number (`float`)
`static void`	`print(int i)` Prints an integer (`int`)
`static void`	`print(long l)` Prints a long integer (`long`)
`static void`	`print(java.lang.Object o)` Prints the `String` representation of an object
`static void`	`print(java.lang.String s)` Prints a character string (`String`)
`static void`	`println()` Prints a new line.
`static void`	`println(boolean b)` Prints a boolean (`boolean`) followed by a newline.
`static void`	`println(char c)` Prints a single character (`char`) followed by a newline.
`static void`	`println(double d)` Prints a double-precision floating point number (`double`) followed by a newline.
`static void`	`println(float f)` Prints a single-precision floating point number (`float`) followed by a newline.
`static void`	`println(int i)` Prints an integer (`int`) followed by a newline.
`static void`	`println(long l)` Prints a long integer (`long`) followed by a newline.
`static void`	`println(java.lang.Object o)` Prints the `String` representation of an object followed by a newline.
`static void`	`println(java.lang.String s)` Prints a character string (`String`) followed by a newline.
`static char`	`readChar()` Reads a character from the keyboard and returns its value.
`static double`	`readDouble()` Reads a lexeme from the input and converts it into a `double`.
`static float`	`readFloat()` Reads a lexeme from the input and converts it into a `float`.
`static int`	`readInt()` Reads a lexeme from the input and converts it into an `int`.
`static java.lang.String`	`readLine()` Read a character string until the next carriage return (end of line).
`static long`	`readLong()` Reads a lexeme from the input and converts it into a `long`.
`static java.lang.String`	`readString()` Reads a lexeme from the input.
`static void`	`setColor(int r, int g, int b)` Sets the color of the subsequent drawing operations.
`static void`	`setGray(int c)` Sets the color of the subsequent drawing operations to be grey.
`static void`	`startDrawings()` Prepares a drawing zone of size 200x200.
`static void`	`startDrawings(int width, int height)` Prepares a drawing zone of arbitrary size.
`static void`	`stopDrawings()` Closes the drawing window.
`static boolean`	`stringToBoolean(java.lang.String s)` Converts a character string into a `boolean`.
`static byte`	`stringToByte(java.lang.String s)` Converts a character string into a `byte`.
`static double`	`stringToDouble(java.lang.String s)` Converts a character string into a `double`.
`static float`	`stringToFloat(java.lang.String s)` Converts a character string into a `float`.
`static int`	`stringToInt(java.lang.String s)` Converts a character string into an `int`.
`static long`	`stringToLong(java.lang.String s)` Converts a character string into a `long`.
`static java.lang.String`	`subString(java.lang.String aString, int begin, int end)` Extracts a substring from a given character string.

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

- Field Detail
  - NO_ERROR
```
public static final  int NO_ERROR
```
    The last I/O operation went well.
    
    See Also:
    Constant Field Values
  - STREAM_ERROR
```
public static final  int STREAM_ERROR
```
    Reading the input stream was impossible.
    
    See Also:
    Constant Field Values
  - FORMAT_ERROR
```
public static final  int FORMAT_ERROR
```
    The conversion of the character string that was read to the needed data type was not possible.
    
    See Also:
    Constant Field Values
  - ARG_ERROR
```
public static final  int ARG_ERROR
```
    The arguments is invalid (ex: ==null).
    
    See Also:
    Constant Field Values
- Method Detail
  - isOk
```
public static  boolean  isOk()
```
    This method return the error state of the last I/o operation.
    
    true
    if everything was fine;
    
    false
    if an error occured. In that case, it is useful to get the error code using getStatus().
    
    Calling this method is equivalent to the expression getStatus()==NO_ERROR.
    
    Returns:
    if an I/O error occured or not.
  - getStatus
```
public static  int  getStatus()
```
    Returns the error code of the last I/O operation.
    
    Returns:
    the error code of the last I/O operation.
  - readChar
```
public static  char  readChar()
```
    Reads a character from the keyboard and returns its value.
    The read bytes come from the standard input.
    
    Returns:
    the character that was entered. If the character is <nul> it is advised to look if the I/O operation was actually successful or not (isOk()).
  - exit
```
public static  void  exit()
```
    Terminates the program.
  - readLine
```
public static  java.lang.String  readLine()
```
    Read a character string until the next carriage return (end of line).
    The characters are read one after the other using the readChar() method.
    
    Returns:
    the next input line.
  - stringToBoolean
```
public static  boolean  stringToBoolean(java.lang.String  s)
```
    Converts a character string into a boolean.
    
    Parameters:
    s - the character string
    
    Returns:
    the value after conversion (boolean)
    
    true
    if s is equal to "true"
    
    false
    otherwise
  - stringToInt
```
public static  int  stringToInt(java.lang.String  s)
```
    Converts a character string into an int.
    In case of an error, the error state is updated.
    
    Parameters:
    s - the character string
    
    Returns:
    the value after conversion (int) Warning: if the returned value is 0, it is necessary to consult the error status of the operation.
  - stringToByte
```
public static  byte  stringToByte(java.lang.String  s)
```
    Converts a character string into a byte.
    In case of an error, the error state is updated.
    
    Parameters:
    s - the character string
    
    Returns:
    the value after conversion (byte) Warning: if the returned value is 0, it is necessary to consult the error status of the operation.
  - stringToDouble
```
public static  double  stringToDouble(java.lang.String  s)
```
    Converts a character string into a double.
    In case of an error, the error state is updated.
    
    Parameters:
    s - the character string
    
    Returns:
    the value after conversion (double) Warning: if the returned value is 0.0, it is necessary to consult the error status of the operation.
  - stringToFloat
```
public static  float  stringToFloat(java.lang.String  s)
```
    Converts a character string into a float.
    In case of an error, the error state is updated.
    
    Parameters:
    s - the character string
    
    Returns:
    the value after conversion (float) Warning: if the returned value is 0.0, it is necessary to consult the error status of the operation.
  - stringToLong
```
public static  long  stringToLong(java.lang.String  s)
```
    Converts a character string into a long.
    In case of an error, the error state is updated.
    
    Parameters:
    s - the character string
    
    Returns:
    the value after conversion (long) Warning: if the returned value is 0, it is necessary to consult the error status of the operation.
  - readInt
```
public static  int  readInt()
```
    Reads a lexeme from the input and converts it into an int.
    In case of an error, the error state is updated.
    
    Returns:
    the next lexeme as an integer (int)
  - readLong
```
public static  long  readLong()
```
    Reads a lexeme from the input and converts it into a long.
    In case of an error, the error state is updated.
    
    Returns:
    the next lexeme as a long integer (long)
  - readFloat
```
public static  float  readFloat()
```
    Reads a lexeme from the input and converts it into a float.
    In case of an error, the error state is updated.
    
    Returns:
    the next lexeme as a single-precision float (float)
  - readDouble
```
public static  double  readDouble()
```
    Reads a lexeme from the input and converts it into a double.
    In case of an error, the error state is updated.
    
    Returns:
    the next lexeme as a double-precision float (double)
  - readString
```
public static  java.lang.String  readString()
```
    Reads a lexeme from the input.
    In case of an error, the error state is updated.
    
    Returns:
    the next lexeme (null in case of failure).
  - print
```
public static  void  print(char  c)
```
    Prints a character.
    
    Parameters:
    c - the character to print.
  - print
```
public static  void  print(int  i)
```
    Prints an integer (int)
    
    Parameters:
    i - the integer to print
  - print
```
public static  void  print(boolean  b)
```
    Prints a boolean (boolean)
    
    Parameters:
    b - the boolean to print
  - print
```
public static  void  print(long  l)
```
    Prints a long integer (long)
    
    Parameters:
    l - the long integer to print
  - print
```
public static  void  print(float  f)
```
    Prints a single-precision floating point number (float)
    
    Parameters:
    f - the float to print
  - print
```
public static  void  print(double  d)
```
    Prints a double-precision flooating point number (double)
    
    Parameters:
    d - the double to print
  - print
```
public static  void  print(java.lang.Object  o)
```
    Prints the String representation of an object
    
    Parameters:
    o - the object to print
  - print
```
public static  void  print(java.lang.String  s)
```
    Prints a character string (String)
    
    Parameters:
    s - the string to print
  - println
```
public static  void  println(char  c)
```
    Prints a single character (char) followed by a newline. A call to this method is equivalent to print(c); println();.
    
    Parameters:
    c - the character to print
  - println
```
public static  void  println(boolean  b)
```
    Prints a boolean (boolean) followed by a newline. A call to this method is equivalent to print(c); println();.
    
    Parameters:
    b - the boolean to print
  - println
```
public static  void  println(int  i)
```
    Prints an integer (int) followed by a newline. A call to this method is equivalent to print(c); println();.
    
    Parameters:
    i - the integer to print
  - println
```
public static  void  println(long  l)
```
    Prints a long integer (long) followed by a newline. A call to this method is equivalent to print(c); println();.
    
    Parameters:
    l - the long integer to print
  - println
```
public static  void  println(float  f)
```
    Prints a single-precision floating point number (float) followed by a newline. A call to this method is equivalent to print(c); println();.
    
    Parameters:
    f - the single-precision float to print
  - println
```
public static  void  println(double  d)
```
    Prints a double-precision floating point number (double) followed by a newline. A call to this method is equivalent to print(c); println();.
    
    Parameters:
    f - the double-precision float to print
  - println
```
public static  void  println(java.lang.Object  o)
```
    Prints the String representation of an object followed by a newline.
    
    Parameters:
    o - the object to print
  - println
```
public static  void  println(java.lang.String  s)
```
    Prints a character string (String) followed by a newline.
    
    Parameters:
    s - the string to print
  - println
```
public static  void  println()
```
    Prints a new line.
  - charAt
```
public static  char  charAt(java.lang.String  aString,
          int  position)
```
    Extracts the character at a given position in a character string.
    
    Parameters:
    aString - the character string
    position - the index of the character to extract
    
    Returns:
    the character at the given position
  - subString
```
public static  java.lang.String  subString(java.lang.String  aString,
                         int  begin,
                         int  end)
```
    Extracts a substring from a given character string.
    
    Parameters:
    aString - the character string
    begin - index of the first character of the substring
    end - index of the first character excluded from the substring
    
    Returns:
    the extracted character string
  - booleanToString
```
public static  java.lang.String  booleanToString(boolean  value)
```
    Converts a boolean to a character string (String).
    
    Parameters:
    value - the boolean (boolean)
    
    Returns:
    the corresponding character string
  - charToString
```
public static  java.lang.String  charToString(char  value)
```
    Converts a character to a character string (String).
    
    Parameters:
    value - the character (char)
    
    Returns:
    the corresponding character string
  - floatToString
```
public static  java.lang.String  floatToString(float  value)
```
    Converts a single-precision floating point number to a character string (String).
    
    Parameters:
    value - the single-precision floating number (float)
    
    Returns:
    the corresponding character string
  - doubleToString
```
public static  java.lang.String  doubleToString(double  value)
```
    Converts a double-precision floating point number to a character string (String).
    
    Parameters:
    value - the double-precision floating number (double)
    
    Returns:
    the corresponding character string
  - intToString
```
public static  java.lang.String  intToString(int  value)
```
    Converts an integer to a character string (String).
    
    Parameters:
    value - the integer (int)
    
    Returns:
    the corresponding character string
  - longToString
```
public static  java.lang.String  longToString(long  value)
```
    Converts a long integer to a character string (String).
    
    Parameters:
    value - the integer (long)
    
    Returns:
    the corresponding character string
  - equals
```
public static  boolean  equals(java.lang.String  aString,
             java.lang.String  anotherString)
```
    Tests the equality between two character strings.
    
    Parameters:
    aString - the first character string
    anotherString - the second character string
    
    Returns:
    true if the two are equal, false otherwise.
  - compare
```
public static  int  compare(java.lang.String  aString,
          java.lang.String  anotherString)
```
    Compares two character strings.
    
    Parameters:
    aString - the first character string
    anotherString - the second character string
    
    Returns:
    0 if the strings are equal; a negative integer if the second is bigger than the first using the lexicographic order (dictionary order); a positive integer if the first string is bigger than the second one.
  - length
```
public static  int  length(java.lang.String  aString)
```
    Computes the length of a given character string.
    
    Parameters:
    aString - the character string
    
    Returns:
    its length as an integer
  - startDrawings
```
public static  void  startDrawings()
```
    Prepares a drawing zone of size 200x200.
  - startDrawings
```
public static  void  startDrawings(int  width,
                 int  height)
```
    Prepares a drawing zone of arbitrary size.
    
    Parameters:
    width - the width of the display
    height - the height of the display
  - stopDrawings
```
public static  void  stopDrawings()
```
    Closes the drawing window.
  - drawPoint
```
public static  void  drawPoint(int  x,
             int  y)
```
    Draws a point in the drawing zone.
    
    Parameters:
    x - the x-coordinate (abscissa)
    y - the y-coordinate (ordinate)
  - setColor
```
public static  void  setColor(int  r,
            int  g,
            int  b)
```
    Sets the color of the subsequent drawing operations. Colors are given using 256 levels of red, green and blue, from 0,0,0 for black to 255,255,255 for white. Red is therefore with 255,0,0, green with 0,255,0 and blue with 0,0,255.
    
    Parameters:
    r - the red level
    g - the green level
    b - the blue level
  - setGray
```
public static  void  setGray(int  c)
```
    Sets the color of the subsequent drawing operations to be grey. There are 256 grey levels, from 0 for black to 255 for white. An average grey would be done with parameter 127.
    
    Parameters:
    c - the grey-level
  - drawLine
```
public static  void  drawLine(int  x0,
            int  y0,
            int  x1,
            int  y1)
```
    Draws a line between two points in the drawing area. Dessine un segment de droite dans la zone d'affichage.
    
    Parameters:
    x0 - the x-coordinate of the first point.
    y0 - the y-coordinate of the first point.
    x1 - the x-coordinate of the second point.
    y1 - the y-coordinate of the second point.
  - drawRect
```
public static  void  drawRect(int  x,
            int  y,
            int  w,
            int  h)
```
    Draws an empty rectangle in the display zone.
    The top-left corner is at coordinates x and y.
    
    Parameters:
    x - the x-coordinate of the top-left corner.
    y - the y-coordinate of the top-left corner.
    w - the width of the rectangle.
    h - the height of the rectangle.
  - fillRect
```
public static  void  fillRect(int  x,
            int  y,
            int  w,
            int  h)
```
    Draws a filled rectangle in the display zone.
    The top-left corner is at coordinates x and y.
    
    Parameters:
    x - the x-coordinate of the top-left corner.
    y - the y-coordinate of the top-left corner.
    w - the width of the rectangle.
    h - the height of the rectangle.
  - drawCircle
```
public static  void  drawCircle(int  x,
              int  y,
              int  r)
```
    Draws a circle in the display zone.
    
    Parameters:
    x - the x-coordinate of the centre of the circle.
    y - the y-coordinate of the centre of the circle.
    r - the circle radius.
  - fillCircle
```
public static  void  fillCircle(int  x,
              int  y,
              int  r)
```
    Draws a filled circle in the display zone.
    
    Parameters:
    x - the x-coordinate of the centre of the circle.
    y - the y-coordinate of the centre of the circle.
    r - the circle radius.
  - drawArc
```
public static  void  drawArc(int  x,
           int  y,
           int  r,
           int  angleInit,
           int  angleCouvert)
```
    Draws an arc in the display zone.
    The angles are in degrees. The direction is counter-clockwise. The initial angle is angleInit and the terminating angle is angleInit + angleCouvert.
    
    Parameters:
    x - the x-coordinate of the centre of the circle.
    y - the y-coordinate of the centre of the circle.
    r - the circle radius.
    angleInit - the initial angle.
    angleCouvert - the angle covered by the arc.
  - fillArc
```
public static  void  fillArc(int  x,
           int  y,
           int  r,
           int  angleInit,
           int  angleCouvert)
```
    Draws an filled arc in the display zone.
    The angles are in degrees. The direction is counter-clockwise. The initial angle is angleInit and the terminating angle is angleInit + angleCouvert.
    
    Parameters:
    x - the x-coordinate of the centre of the circle.
    y - the y-coordinate of the centre of the circle.
    r - the circle radius.
    angleInit - the initial angle.
    angleCouvert - the angle covered by the arc.
  - clearArea
```
public static  void  clearArea()
```
    Clears the diplay area completely.

Rhul

Class Rhul

Input/Outputs (I/O)

Drawings

String operations

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

NO_ERROR

STREAM_ERROR

FORMAT_ERROR

ARG_ERROR

Method Detail

isOk

getStatus

readChar

exit

readLine

stringToBoolean

stringToInt

stringToByte

stringToDouble

stringToFloat

stringToLong

readInt

readLong

readFloat

readDouble

readString

print

print

print

print

print

print

print

print

println

println

println

println

println

println

println

println

println

charAt

subString

booleanToString

charToString

floatToString

doubleToString

intToString

longToString

equals

compare

length

startDrawings

startDrawings

stopDrawings

drawPoint

setColor

setGray

drawLine

drawRect

fillRect

drawCircle

fillCircle

drawArc

fillArc

clearArea