com.numericalmethod.suanshu.number

Class NumberUtils

java.lang.Object

com.numericalmethod.suanshu.number.NumberUtils

public class NumberUtils
extends java.lang.Object

These are the utility functions to manipulate Numbers.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	NumberUtils.Comparable<T extends java.lang.Number> We need a precision parameter to determine whether two numbers are close enough to be treated as equal.

Method Summary

Modifier and Type	Method and Description
static int	compare(java.lang.Number num1, java.lang.Number num2, double epsilon) Compare two numbers.
static boolean	equal(java.lang.Number num1, java.lang.Number num2, double epsilon) Check the equality of two Numbers, up to a precision.
static boolean	isReal(java.lang.Number number) Check if a number is a real number.
static java.lang.Number	parse(java.lang.String str) Construct a number from a String.
static java.lang.Number[]	parseArray(java.lang.String... strs) Convert an array of numbers in String to an array of numbers in Number.

Methods inherited from class java.lang.Object

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

Method Detail

equal

public static boolean equal(java.lang.Number num1,
                            java.lang.Number num2,
                            double epsilon)

Check the equality of two Numbers, up to a precision.

Parameters:

num1 - a number

num2 - a number

epsilon - a precision parameter: when a number |x| ≤ ε, it is considered 0

Returns:

true if the numbers are close enough, false otherwise

compare

public static int compare(java.lang.Number num1,
                          java.lang.Number num2,
                          double epsilon)

Compare two numbers. The two numbers must be of (possibly different) subclasses of Number.

• If both can be cast to double, they are compared as doubles; e.g., 2 vs. new Double(3);
• If one is a double but the other is not, the double is cast into the same field as the other number for comparison; e.g., 4 vs. 3 + 0i;
• If neither is a double, the two numbers must be of the same class for comparison; e.g., both are Complex.

Parameters:

num1 - a number

num2 - a number

epsilon - a precision parameter: when a number |x| ≤ ε, it is considered 0; e.g., 1e-9

Returns:

0 if num1 is close enough to num2; 1 if num1 > num2; -1 if num1 < num2

isReal

public static boolean isReal(java.lang.Number number)

Check if a number is a real number.

TODO: this function needs to be extended or modified when a new Number subclass is implemented.

Parameters:

number - a number

Returns:

true if the number is real, i.e., in Rⁿ

parse

public static java.lang.Number parse(java.lang.String str)

Construct a number from a String. For example, some valid strings are:

 "2"
 "2."
 "3 + 5i"
 "1.23 - 4.56i"
 "-1.23 - 4.56i"
 "-1.23 - 4.56e-7i"
 "-1.23 - 4.56+e7i"
 "i"
 

Note: having spaces in the real part between sign and number is illegal, e.g.,

 - 1.23+4.56i
 + 1.23+4.56i
 

TODO: this function needs to be extended or modified when a new Number subclass is implemented.

Parameters:

str - a number in String

Returns:

a number of type subclass-ing from Number, such as Double, Complex

parseArray

public static java.lang.Number[] parseArray(java.lang.String... strs)

Convert an array of numbers in String to an array of numbers in Number.

Parameters:

strs - an array of numbers in String

Returns:

an array of Numbers