org.modeshape.search.lucene
Class FieldUtil

java.lang.Object
  extended by org.modeshape.search.lucene.FieldUtil

public class FieldUtil
extends Object

Utility for working with Lucene field values.


Method Summary
static String decimalToString(BigDecimal value)
          Creates a canonical string representation of the supplied BigDecimal value, whereby all string representations are lexicographically sortable.
protected static String negate(String value)
          Compute the "negated" string, which replaces the digits (0 becomes 9, 1 becomes 8, ... and 9 becomes 0).
protected static StringBuilder negate(StringBuilder value)
          Compute the "negated" string, which replaces the digits (0 becomes 9, 1 becomes 8, ... and 9 becomes 0).
protected static void removeTralingZeros(StringBuilder sb)
          Utility to remove the trailing 0's.
static BigDecimal stringToDecimal(String value)
          Converts the canonical string representation of a BigDecimal value into the object form.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

decimalToString

public static String decimalToString(BigDecimal value)
Creates a canonical string representation of the supplied BigDecimal value, whereby all string representations are lexicographically sortable. This makes it possible to store the wide range of values that can be represented by BigDecimal, while still enabling sorting and range queries.

This canonical form represents all decimal values using a prescribed format, which is based upon Steven Rowe's suggestion but with modifications to handle variable-length exponents (per his suggestion in the last sentence), use spaces between fields on where required (for minimal length), and utilize an optimized (e.g., shorter) form when the value is '0' or the exponent is '0'. Thus, this format contains only digits (e.g., '0'..'9') and the '-' character.

     <significand-sign><exponent-sign><exponent-length> <exponent><significand>
 
where: Thus the fields are defined as: In the case of a negative significand, the <significand> field is negated such that each digit is replaced with (base - digit - 1) and appended by 'A' (which is greater than all other digits) to ensure that significands with greater precision are ordered before those that share significand prefixes but have lesser precision.

Thus, the format for a negative BigDecimal value becomes:

     -<reversed-exponent-sign><negated-exponent-length> <negated-exponent><significand><sentinel>
 
where the <sentinel> is always 'A'. Note that the exponent length field is also negated.

Examples

Here are several examples that show BigDecimal values and their corresponding canonical string representation:

    +5.E-3     => 1-1 65
    +1.E-2     => 1-1 71
    +1.0E-2    => 1-1 71
    +1.0000E-2 => 1-1 71
    +1.1E-2    => 1-1 711
    +1.11E-2   => 1-1 7111
    +1.2E-2    => 1-1 712
    +5.E-2     => 1-1 75
    +7.3E+2    => 111 273
    +7.4E+2    => 111 274
    +7.45E+2   => 111 2745
    +8.7654E+3 => 111 387654
 
Here is how a BigDecimal value of zero is represented:
     0.0E0     => 0
 
BigDecimal values with an exponent of '0' are represented as follows:
    +1.2E0     => 1012
    -1.2E0     => -087A
 
And here are some negative value examples:
    -8.7654E+3 => --8 612345A
    -7.45E+2   => --8 7254A
    -7.4E+2    => --8 725A
    -7.3E+2    => --8 726A
    -5.E-2     => -18 24A
    -1.2E-2    => -18 287A
    -1.11E-2   => -18 2888A
    -1.1E-2    => -18 288A
    -1.0000E-2 => -18 28A
    -1.0E-2    => -18 28A
    -1.E-2     => -18 28A
    -5.E-3     => -18 34A
    -5.E-4     => -18 44A
 

This canonical form is valid for all values of BigDecimal.

Parameters:
value - the value to be converted into its canonical form; may not be null
Returns:
the canonical string representation; never null or empty
See Also:
stringToDecimal(String)

stringToDecimal

public static BigDecimal stringToDecimal(String value)
Converts the canonical string representation of a BigDecimal value into the object form.

See decimalToString(BigDecimal) to documentation of the canonical form.

Parameters:
value - the canonical string representation; may not be null or empty
Returns:
the BigDecimal representation; never null
See Also:
decimalToString(BigDecimal)

negate

protected static String negate(String value)
Compute the "negated" string, which replaces the digits (0 becomes 9, 1 becomes 8, ... and 9 becomes 0).

Parameters:
value - the input string; may not be null
Returns:
the negated string; never null
See Also:
negate(StringBuilder)

negate

protected static StringBuilder negate(StringBuilder value)
Compute the "negated" string, which replaces the digits (0 becomes 9, 1 becomes 8, ... and 9 becomes 0).

Parameters:
value - the input string; may not be null
Returns:
the negated string; never null
See Also:
negate(String)

removeTralingZeros

protected static void removeTralingZeros(StringBuilder sb)
Utility to remove the trailing 0's.

Parameters:
sb - the input string builder; may not be null


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