org.qbroker.common

Class Evaluation

java.lang.Object

org.qbroker.common.Evaluation

public class Evaluation
extends java.lang.Object

Evaluation evaluates a simple numeric expression, or a boolean expression with either numbers or single quoted strings, or a ternary expression for either numbers or single quoted strings. In case of the numeric expression, it supports 5 basic numeric operations, such as addition, substruction, multiplication, division, and modulation. For a boolean expression, it supports basic numeric comparisons and 4 string comparisons for single quoted strings, such as "==", "!=", "=~" and "!~". The match operation is based on String.match().

There are 3 public methods, evaluate(), choose() and isStringExpression(). They all take a text as the input expression. The first returns either a Long or a Double for a numeric expression, or an Integer for a boolean expression. In case of a boolean expression, Integer 1 is for true and Integer 0 for false. The second evaluates a ternary expression with a boolan expression and two single quoted strings. It returns one of the quoted strings based on evaluation of the boolean experssion. The last returns true if the expression is a ternary expression for single quoted strings, or false otherwise.

Author:

yannanlu@yahoo.com

Method Summary

Modifier and Type	Method and Description
static java.lang.String	choose(java.lang.String expr) It evaluates a ternary expression with a boolean expression and two single quoted strings and returns one of the strings with quotes as the result upon success.
static java.lang.Number	evaluate(java.lang.String expr) It evaluates a numeric expression or a boolean expression and returns a Number as the result up on success.
static boolean	isStringExpression(java.lang.String expr) returns true if expression is a ternary expression for quoted strings
static void	main(java.lang.String[] args)
static java.lang.String	unquote(java.lang.String expr)

Methods inherited from class java.lang.Object

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

Method Detail

evaluate

public static java.lang.Number evaluate(java.lang.String expr)

It evaluates a numeric expression or a boolean expression and returns a Number as the result up on success. Otherwise it returns a null or throws an IllegalArgumentException for failure. For a numeric expression, the result is either a Long or a Double. In case of a boolean expression, the result is an Integer of either 1 for TRUE or 0 for FALSE.

choose

public static java.lang.String choose(java.lang.String expr)

It evaluates a ternary expression with a boolean expression and two single quoted strings and returns one of the strings with quotes as the result upon success. Otherwise it returns null or just throws an IllegalArgumentException to indicate failure. Any single quoted string can be replaced by a ternary expression as long as its result is also a single quoted string.

isStringExpression

public static boolean isStringExpression(java.lang.String expr)

returns true if expression is a ternary expression for quoted strings

unquote

public static java.lang.String unquote(java.lang.String expr)

main

public static void main(java.lang.String[] args)