org.modeshape.jcr.query.lucene
Class FieldUtil

java.lang.Object
  org.modeshape.jcr.query.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 '-' and 'A' characters.

     <significand-sign><exponent-sign><exponent-length> <exponent><significand>
 

where:

• the significand is the part of the number containing the significant figures, and is a (big) integer value obtained from the BigDecimal using BigDecimal.unscaledValue();
• the exponent is the integer used to define the number of factors of 10 that are applied to the significand, obtained by computing value.precision() - value.scale() - 1;

Thus the fields are defined as:

• the <significand-sign> is '-' if the significand is negative, '0' if equal to zero, or '1' if positive;
• the <exponent-sign> is '-' if the exponent is negative, '0' if equal to zero, or '1' if positive; if '0', then the <exponent-length> and <exponent> fields are not written;
• the <exponent-length> is the postive value representing the length of the <exponent>, and is not included when the <exponent-sign> is '0';
• the <exponent> is the integer used to define the number of factors of 10 that are applied to the significand, obtained by computing value.precision() - value.scale() - 1;
• the <significand> is the part of the number containing the significant figures, and is a (big) integer value obtained from the BigDecimal using BigDecimal.unscaledValue();

In the case of a negative exponent, the <exponent-length> field is negated such that each digit is replaced with (base - digit - 1).

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. In this case, the <exponent-length> and <exponent> parts are also negated (unless they already are).

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     => 1-8 65
    +1.E-2     => 1-8 71
    +1.0E-2    => 1-8 71
    +1.0000E-2 => 1-8 71
    +1.1E-2    => 1-8 711
    +1.11E-2   => 1-8 7111
    +1.2E-2    => 1-8 712
    +5.E-2     => 1-8 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