com.google.visualization.datasource.query.scalarfunction
Class Difference

java.lang.Object
  com.google.visualization.datasource.query.scalarfunction.Difference

All Implemented Interfaces:

ScalarFunction

public class Difference
extends java.lang.Object
implements ScalarFunction

The binary scalar function difference(). Returns the difference between two number values.

Author:

Liron L.

Method Summary

Value	evaluate(java.util.List<Value> values) Executes the scalar function difference() on the given values.
java.lang.String	getFunctionName() Returns the function's name.
static Difference	getInstance() Returns the singleton instance of this class.
ValueType	getReturnType(java.util.List<ValueType> types) Returns the return type of the function.
java.lang.String	toQueryString(java.util.List<java.lang.String> argumentsQueryStrings) Returns a string that when given to the query parser will yield a similar scalar function.
void	validateParameters(java.util.List<ValueType> types) Validates that all function parameters are of type NUMBER, and that there are exactly 2 parameters.

Methods inherited from class java.lang.Object

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

Method Detail

getInstance

public static Difference getInstance()

Returns the singleton instance of this class.

Returns:

The singleton instance of this class.

getFunctionName

public java.lang.String getFunctionName()

Returns the function's name.

Specified by:

getFunctionName in interface ScalarFunction

Returns:

The function's name.

evaluate

public Value evaluate(java.util.List<Value> values)

Executes the scalar function difference() on the given values. Returns the difference between the given values. All values are number values. The method does not validate the parameters, the user must check the parameters before calling this method.

Specified by:

evaluate in interface ScalarFunction

Parameters:

values - A list of the values on which the scalar function will be performed.

Returns:

Value with the difference of all given values, or number null value if one of the values is null.

getReturnType

public ValueType getReturnType(java.util.List<ValueType> types)

Returns the return type of the function. In this case, NUMBER. The method does not validate the parameters, the user must check the parameters before calling this method.

Specified by:

getReturnType in interface ScalarFunction

Parameters:

types - A list of the types of the scalar function parameters.

Returns:

The type of the returned value: Number.

validateParameters

public void validateParameters(java.util.List<ValueType> types)
                        throws InvalidQueryException

Validates that all function parameters are of type NUMBER, and that there are exactly 2 parameters. Throws a ScalarFunctionException otherwise.

Specified by:

validateParameters in interface ScalarFunction

Parameters:

types - A list with parameters types.

Throws:

InvalidQueryException - Thrown if the parameters are invalid.

toQueryString

public java.lang.String toQueryString(java.util.List<java.lang.String> argumentsQueryStrings)

Returns a string that when given to the query parser will yield a similar scalar function. Takes as arguments the query strings of the arguments.

Specified by:

toQueryString in interface ScalarFunction

Parameters:

argumentsQueryStrings - The query strings of the actual arguments.

Returns:

The query string.