| This class contains the logic for coercing data types before
operators are applied to them.
The following is the list of rules applied for various type
conversions.
Applying arithmetic operator
Binary operator - A {+,-,*} B
if A and B are null
return 0
if A or B is BigDecimal, coerce both to BigDecimal and then:
if operator is +, return A.add(B)
if operator is -, return A.subtract(B)
if operator is *, return A.multiply(B)
if A or B is Float, Double, or String containing ".", "e", or "E"
if A or B is BigInteger, coerce both A and B to BigDecimal and apply operator
coerce both A and B to Double and apply operator
if A or B is BigInteger, coerce both to BigInteger and then:
if operator is +, return A.add(B)
if operator is -, return A.subtract(B)
if operator is *, return A.multiply(B)
otherwise
coerce both A and B to Long
apply operator
if operator results in exception (such as divide by 0), error
Binary operator - A {/,div} B
if A and B are null
return 0
if A or B is a BigDecimal or BigInteger, coerce both to BigDecimal and
return A.divide(B, BigDecimal.ROUND_HALF_UP)
otherwise
coerce both A and B to Double
apply operator
if operator results in exception (such as divide by 0), error
Binary operator - A {%,mod} B
if A and B are null
return 0
if A or B is BigDecimal, Float, Double, or String containing ".", "e" or "E"
coerce both to Double
apply operator
if A or B is BigInteger, coerce both to BigInteger and return
A.remainder(B)
otherwise
coerce both A and B to Long
apply operator
if operator results in exception (such as divide by 0), error
Unary minus operator - -A
if A is null
return 0
if A is BigInteger or BigDecimal, return A.negate()
if A is String
if A contains ".", "e", or "E"
coerce to Double, apply operator
otherwise
coerce to a Long and apply operator
if A is Byte,Short,Integer,Long,Float,Double
retain type, apply operator
if operator results in exception, error
otherwise
error
Applying "empty" operator - empty A
if A is null
return true
if A is zero-length String
return true
if A is zero-length array
return true
if A is List and ((List) A).isEmpty()
return true
if A is Map and ((Map) A).isEmpty()
return true
if A is Collection an ((Collection) A).isEmpty()
return true
otherwise
return false
Applying logical operators
Binary operator - A {and,or} B
coerce both A and B to Boolean, apply operator
NOTE - operator stops as soon as expression can be determined, i.e.,
A and B and C and D - if B is false, then only A and B is evaluated
Unary not operator - not A
coerce A to Boolean, apply operator
Applying relational operator
A {<,>,<=,>=,lt,gt,lte,gte} B
if A==B
if operator is >= or <=
return true
otherwise
return false
if A or B is null
return false
if A or B is BigDecimal, coerce both A and B to BigDecimal and use the
return value of A.compareTo(B)
if A or B is Float or Double
coerce both A and B to Double
apply operator
if A or B is BigInteger, coerce both A and B to BigInteger and use the
return value of A.compareTo(B)
if A or B is Byte,Short,Character,Integer,Long
coerce both A and B to Long
apply operator
if A or B is String
coerce both A and B to String, compare lexically
if A is Comparable
if A.compareTo (B) throws exception
error
otherwise
use result of A.compareTo(B)
if B is Comparable
if B.compareTo (A) throws exception
error
otherwise
use result of B.compareTo(A)
otherwise
error
Applying equality operator
A {==,!=} B
if A==B
apply operator
if A or B is null
return false for ==, true for !=
if A or B is BigDecimal, coerce both A and B to BigDecimal and then:
if operator is == or eq, return A.equals(B)
if operator is != or ne, return !A.equals(B)
if A or B is Float or Double
coerce both A and B to Double
apply operator
if A or B is BigInteger, coerce both A and B to BigInteger and then:
if operator is == or eq, return A.equals(B)
if operator is != or ne, return !A.equals(B)
if A or B is Byte,Short,Character,Integer,Long
coerce both A and B to Long
apply operator
if A or B is Boolean
coerce both A and B to Boolean
apply operator
if A or B is String
coerce both A and B to String, compare lexically
otherwise
if an error occurs while calling A.equals(B)
error
apply operator to result of A.equals(B)
coercions
coerce A to String
A is String
return A
A is null
return ""
A.toString throws exception
error
otherwise
return A.toString
coerce A to Number type N
A is null or ""
return 0
A is Character
convert to short, apply following rules
A is Boolean
error
A is Number type N
return A
A is Number, coerce quietly to type N using the following algorithm
If N is BigInteger
If A is BigDecimal, return A.toBigInteger()
Otherwise, return BigInteger.valueOf(A.longValue())
if N is BigDecimal
If A is a BigInteger, return new BigDecimal(A)
Otherwise, return new BigDecimal(A.doubleValue())
If N is Byte, return new Byte(A.byteValue())
If N is Short, return new Short(A.shortValue())
If N is Integer, return new Integer(A.integerValue())
If N is Long, return new Long(A.longValue())
If N is Float, return new Float(A.floatValue())
If N is Double, return new Double(A.doubleValue())
otherwise ERROR
A is String
If N is BigDecimal then:
If new BigDecimal(A) throws an exception then ERROR
Otherwise, return new BigDecimal(A)
If N is BigInteger then:
If new BigInteger(A) throws an exception, then ERROR
Otherwise, return new BigInteger(A)
new N.valueOf(A) throws exception
error
return N.valueOf(A)
otherwise
error
coerce A to Character should be
A is null or ""
return (char) 0
A is Character
return A
A is Boolean
error
A is Number with less precision than short
coerce quietly - return (char) A
A is Number with greater precision than short
coerce quietly - return (char) A
A is String
return A.charAt (0)
otherwise
error
coerce A to Boolean
A is null or ""
return false
A is Boolean
return A
A is String
Boolean.valueOf(A) throws exception
error
return Boolean.valueOf(A)
otherwise
error
coerce A to any other type T
A is null
return null
A is assignable to T
coerce quietly
A is String
T has no PropertyEditor
if A is "", return null
otherwise error
T's PropertyEditor throws exception
if A is "", return null
otherwise error
otherwise
apply T's PropertyEditor
otherwise
error
author:
Nathan Abramson - Art Technology Group
version:
$Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author$ |
