org.rrd4j.core
Class Util

java.lang.Object
  org.rrd4j.core.Util

public class Util
extends Object

Class defines various utility functions used in Rrd4j.

Author:

Sasa Markovic

Nested Class Summary

static class

Util.Xml Various DOM utility functions.

Field Summary

static double	MAX_DOUBLE
static long	MAX_LONG
static double	MIN_DOUBLE
static long	MIN_LONG

Constructor Summary

Util()

Method Summary

static boolean	equal(double x, double y) Compares two doubles but treats all NaNs as equal.
static boolean	fileExists(String filename) Checks if the file with the given file name exists
static String	formatDouble(double x) Formats double as a string using exponential notation (RRDTool like).
static Calendar	getCalendar(Date date) Returns Calendar object for the given Date object
static Calendar	getCalendar(long timestamp) Returns Calendar object for the given timestamp (in seconds, without milliseconds)
static Calendar	getCalendar(String timeStr) Creates Calendar object from a string.
static String	getCanonicalPath(String path) Returns canonical file path for the given file path
static Date	getDate(long timestamp) Returns Date object for the given timestamp (in seconds, without milliseconds)
static String	getFileSeparator() Returns file system separator string.
static String	getLapTime() Function used for debugging purposes and performance bottlenecks detection.
static long	getLastModified(String file) Returns last modification time for the given file.
static String	getRrd4jDemoDirectory() Returns path to directory used for placement of Rrd4j demo graphs and creates it if necessary.
static String	getRrd4jDemoPath(String filename) Returns full path to the file stored in the demo directory of Rrd4j
static String	getRrd4jHomeDirectory() Returns the root directory of the Rrd4j distribution.
static long	getTime() Returns current timestamp in seconds (without milliseconds).
static long	getTimestamp() Just an alias for getTime() method.
static long	getTimestamp(Calendar gc) Returns timestamp (unix epoch) for the given Calendar object
static long	getTimestamp(Date date) Returns timestamp (unix epoch) for the given Date object
static long	getTimestamp(int year, int month, int day) Returns timestamp (unix epoch) for the given year, month and day.
static long	getTimestamp(int year, int month, int day, int hour, int min) Returns timestamp (unix epoch) for the given year, month, day, hour and minute.
static long	getTimestamp(String atStyleTimeSpec) Parses at-style time specification and returns the corresponding timestamp.
static long[]	getTimestamps(String atStyleTimeSpec1, String atStyleTimeSpec2) Parses two related at-style time specifications and returns corresponding timestamps.
static String	getUserHomeDirectory() Returns path to user's home directory.
static boolean	isDouble(String s) Checks if a string can be parsed as double.
static double	max(double[] values) Finds max value for an array of doubles (NaNs are ignored).
static double	max(double x, double y) Returns the greater of two double values, but treats NaN as the smallest possible value.
static double	min(double[] values) Finds min value for an array of doubles (NaNs are ignored).
static double	min(double x, double y) Returns the smaller of two double values, but treats NaN as the greatest possible value.
static long	normalize(long timestamp, long step) Rounds the given timestamp to the nearest whole "e;step"e;.
static boolean	parseBoolean(String valueStr) Parses input string as a boolean value.
static Paint	parseColor(String valueStr) Parses input string as color.
static double	parseDouble(String valueStr) Parses input string as a double value.
static String	sprintf(String format, Object... args) Equivalent of the C-style sprintf function.
static double	sum(double x, double y) Calculates sum of two doubles, but treats NaNs as zeros.
static double[]	toDoubleArray(long[] array) Converts an array of long primitives to an array of doubles.

Methods inherited from class java.lang.Object

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

Field Detail

MAX_LONG

public static final long MAX_LONG

See Also:

Constant Field Values

MIN_LONG

public static final long MIN_LONG

See Also:

Constant Field Values

MAX_DOUBLE

public static final double MAX_DOUBLE

See Also:

Constant Field Values

MIN_DOUBLE

public static final double MIN_DOUBLE

See Also:

Constant Field Values

Constructor Detail

Util

public Util()

Method Detail

toDoubleArray

public static double[] toDoubleArray(long[] array)

Converts an array of long primitives to an array of doubles.

Returns:

Same array but with all values as double.

getTime

public static long getTime()

Returns current timestamp in seconds (without milliseconds). Returned timestamp is obtained with the following expression:

(System.currentTimeMillis() + 500L) / 1000L

Returns:

Current timestamp

getTimestamp

public static long getTimestamp()

Just an alias for getTime() method.

Returns:

Current timestamp (without milliseconds)

normalize

public static long normalize(long timestamp,
                             long step)

Rounds the given timestamp to the nearest whole "e;step"e;. Rounded value is obtained from the following expression:

timestamp - timestamp % step;

Parameters:

timestamp - Timestamp in seconds

step - Step in seconds

Returns:

"Rounded" timestamp

max

public static double max(double x,
                         double y)

Returns the greater of two double values, but treats NaN as the smallest possible value. Note that Math.max() behaves differently for NaN arguments.

Parameters:

x - an argument

y - another argument

Returns:

the lager of arguments

min

public static double min(double x,
                         double y)

Returns the smaller of two double values, but treats NaN as the greatest possible value. Note that Math.min() behaves differently for NaN arguments.

Parameters:

x - an argument

y - another argument

Returns:

the smaller of arguments

sum

public static double sum(double x,
                         double y)

Calculates sum of two doubles, but treats NaNs as zeros.

Parameters:

x - First double

y - Second double

Returns:

Sum(x,y) calculated as Double.isNaN(x)? y: Double.isNaN(y)? x: x + y;

formatDouble

public static String formatDouble(double x)

Formats double as a string using exponential notation (RRDTool like). Used for debugging through the project.

Parameters:

x - value to be formatted

Returns:

string like "+1.234567E+02"

getDate

public static Date getDate(long timestamp)

Returns Date object for the given timestamp (in seconds, without milliseconds)

Parameters:

timestamp - Timestamp in seconds.

Returns:

Corresponding Date object.

getCalendar

public static Calendar getCalendar(long timestamp)

Returns Calendar object for the given timestamp (in seconds, without milliseconds)

Parameters:

timestamp - Timestamp in seconds.

Returns:

Corresponding Calendar object.

getCalendar

public static Calendar getCalendar(Date date)

Returns Calendar object for the given Date object

Parameters:

date - Date object

Returns:

Corresponding Calendar object.

getTimestamp

public static long getTimestamp(Date date)

Returns timestamp (unix epoch) for the given Date object

Parameters:

date - Date object

Returns:

Corresponding timestamp (without milliseconds)

getTimestamp

public static long getTimestamp(Calendar gc)

Returns timestamp (unix epoch) for the given Calendar object

Parameters:

gc - Calendar object

Returns:

Corresponding timestamp (without milliseconds)

getTimestamp

public static long getTimestamp(int year,
                                int month,
                                int day,
                                int hour,
                                int min)

Returns timestamp (unix epoch) for the given year, month, day, hour and minute.

Parameters:

year - Year

month - Month (zero-based)

day - Day in month

hour - Hour

min - Minute

Returns:

Corresponding timestamp

getTimestamp

public static long getTimestamp(int year,
                                int month,
                                int day)

Returns timestamp (unix epoch) for the given year, month and day.

Parameters:

year - Year

month - Month (zero-based)

day - Day in month

Returns:

Corresponding timestamp

getTimestamp

public static long getTimestamp(String atStyleTimeSpec)

Parses at-style time specification and returns the corresponding timestamp. For example:

 long t = Util.getTimestamp("now-1d");
 

Parameters:

atStyleTimeSpec - at-style time specification. For the complete explanation of the syntax allowed see RRDTool's rrdfetch man page.

Returns:

timestamp in seconds since epoch.

getTimestamps

public static long[] getTimestamps(String atStyleTimeSpec1,
                                   String atStyleTimeSpec2)

Parses two related at-style time specifications and returns corresponding timestamps. For example:

 long[] t = Util.getTimestamps("end-1d","now");
 

Parameters:

atStyleTimeSpec1 - Starting at-style time specification. For the complete explanation of the syntax allowed see RRDTool's rrdfetch man page.

atStyleTimeSpec2 - Ending at-style time specification. For the complete explanation of the syntax allowed see RRDTool's rrdfetch man page.

Returns:

An array of two longs representing starting and ending timestamp in seconds since epoch.

parseDouble

public static double parseDouble(String valueStr)

Parses input string as a double value. If the value cannot be parsed, Double.NaN is returned (NumberFormatException is never thrown).

Parameters:

valueStr - String representing double value

Returns:

a double corresponding to the input string

isDouble

public static boolean isDouble(String s)

Checks if a string can be parsed as double.

Parameters:

s - Input string

Returns:

true if the string can be parsed as double, false otherwise

parseBoolean

public static boolean parseBoolean(String valueStr)

Parses input string as a boolean value. The parser is case insensitive.

Parameters:

valueStr - String representing boolean value

Returns:

true, if valueStr equals to 'true', 'on', 'yes', 'y' or '1'; false in all other cases.

parseColor

public static Paint parseColor(String valueStr)

Parses input string as color. The color string should be of the form #RRGGBB (no alpha specified, opaque color) or #RRGGBBAA (alpa specified, transparent colors). Leading character '#' is optional.

Parameters:

valueStr - Input string, for example #FFAA24, #AABBCC33, 010203 or ABC13E4F

Returns:

Paint object

Throws:

IllegalArgumentException - If the input string is not 6 or 8 characters long (without optional '#')

getFileSeparator

public static String getFileSeparator()

Returns file system separator string.

Returns:

File system separator ("/" on Unix, "\" on Windows)

getUserHomeDirectory

public static String getUserHomeDirectory()

Returns path to user's home directory.

Returns:

Path to users home directory, with file separator appended.

getRrd4jDemoDirectory

public static String getRrd4jDemoDirectory()

Returns path to directory used for placement of Rrd4j demo graphs and creates it if necessary.

Returns:

Path to demo directory (defaults to $HOME/rrd4j/) if directory exists or was successfully created. Null if such directory could not be created.

getRrd4jDemoPath

public static String getRrd4jDemoPath(String filename)

Returns full path to the file stored in the demo directory of Rrd4j

Parameters:

filename - Partial path to the file stored in the demo directory of Rrd4j (just name and extension, without parent directories)

Returns:

Full path to the file

getCalendar

public static Calendar getCalendar(String timeStr)

Creates Calendar object from a string. The string should represent either a long integer (UNIX timestamp in seconds without milliseconds, like "1002354657") or a human readable date string in the format "yyyy-MM-dd HH:mm:ss" (like "2004-02-25 12:23:45").

Parameters:

timeStr - Input string

Returns:

Calendar object

getLapTime

public static String getLapTime()

Function used for debugging purposes and performance bottlenecks detection. Probably of no use for end users of Rrd4j.

Returns:

String representing time in seconds since last getLapTime() method call.

getRrd4jHomeDirectory

public static String getRrd4jHomeDirectory()

Returns the root directory of the Rrd4j distribution. Useful in some demo applications, probably of no use anywhere else.

The function assumes that all Rrd4j .class files are placed under the <root>/classes subdirectory and that all jars (libraries) are placed in the <root>/lib subdirectory (the original Rrd4j directory structure).

Returns:

absolute path to Rrd4j's home directory

equal

public static boolean equal(double x,
                            double y)

Compares two doubles but treats all NaNs as equal. In Java (by default) Double.NaN == Double.NaN always returns false

Parameters:

x - the first value

y - the second value

Returns:

true if x and y are both equal to Double.NaN, or if x == y. false otherwise

getCanonicalPath

public static String getCanonicalPath(String path)
                               throws IOException

Returns canonical file path for the given file path

Parameters:

path - Absolute or relative file path

Returns:

Canonical file path

Throws:

IOException - Thrown if canonical file path could not be resolved

getLastModified

public static long getLastModified(String file)

Returns last modification time for the given file.

Parameters:

file - File object representing file on the disk

Returns:

Last modification time in seconds (without milliseconds)

fileExists

public static boolean fileExists(String filename)

Checks if the file with the given file name exists

Parameters:

filename - File name

Returns:

true if file exists, false otherwise

max

public static double max(double[] values)

Finds max value for an array of doubles (NaNs are ignored). If all values in the array are NaNs, NaN is returned.

Parameters:

values - Array of double values

Returns:

max value in the array (NaNs are ignored)

min

public static double min(double[] values)

Finds min value for an array of doubles (NaNs are ignored). If all values in the array are NaNs, NaN is returned.

Parameters:

values - Array of double values

Returns:

min value in the array (NaNs are ignored)

sprintf

public static String sprintf(String format,
                             Object... args)

Equivalent of the C-style sprintf function.

Parameters:

format - Format string

args - Arbitrary list of arguments

Returns:

Formatted string