org.vanilladb.core.sql

Class Constant

java.lang.Object

org.vanilladb.core.sql.Constant

All Implemented Interfaces:

Comparable<Constant>

Direct Known Subclasses:

BigIntConstant, DoubleConstant, IntegerConstant, VarcharConstant

public abstract class Constant
extends Object
implements Comparable<Constant>

An abstract class that denotes a value of a supported type.

Constructor Summary

Constructors

Constructor and Description
Constant()

Method Summary

Modifier and Type	Method and Description
abstract Constant	add(Constant c) Adds this constant a value specified by another constant.
abstract byte[]	asBytes() Returns the byte array corresponding to this constant value.
abstract Object	asJavaVal() Returns the Java object corresponding to this constant.
abstract Constant	castTo(Type type) Casts this constant to the specified type.
static Constant	defaultInstance(Type type) Constructs a new instance of the specified type with default value.
abstract Constant	div(Constant c) Divides this constant by a value specified by another constant.
abstract Type	getType() Returns the type corresponding to this constant.
abstract Constant	mul(Constant c) Multiplies this constant by a value specified by another constant.
static Constant	newInstance(Type type, byte[] val) Constructs a new instance of the specified type with value converted from the input byte array.
abstract int	size() Return the number of bytes required to encode this constant.
abstract Constant	sub(Constant c) Subtracts a value specified by another constant from this constant.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Comparable

compareTo

Constructor Detail

Constant

public Constant()

Method Detail

newInstance

public static Constant newInstance(Type type,
                                   byte[] val)

Constructs a new instance of the specified type with value converted from the input byte array.

Parameters:

type - the specified type

val - the byte array contains the value

Returns:

a constant of specified type with value converted from the byte array

defaultInstance

public static Constant defaultInstance(Type type)

Constructs a new instance of the specified type with default value. For all numeric constants, the default value is 0; for string constants, the default value is an empty string.

Parameters:

type - the specified type

Returns:

the constant of specified type with default value

getType

public abstract Type getType()

Returns the type corresponding to this constant.

Returns:

the type of the constant

asJavaVal

public abstract Object asJavaVal()

Returns the Java object corresponding to this constant.

Returns:

the Java value of the constant

asBytes

public abstract byte[] asBytes()

Returns the byte array corresponding to this constant value.

Returns:

the byte array of the constant

size

public abstract int size()

Return the number of bytes required to encode this constant.

Returns:

the size of the this constant

castTo

public abstract Constant castTo(Type type)

Casts this constant to the specified type. Does not support casting from a string constant to a numeric constant.

Parameters:

type - the type the caller intends to cast to

Returns:

the constant casted to the specified type

add

public abstract Constant add(Constant c)

Adds this constant a value specified by another constant. Does not support adding value to a string constant. Automatic type upgrade will be done during the arithmetic.

Parameters:

c - constant whose value will be added

Returns:

a constant with value equals to the sum of the value of this constant and another constant

sub

public abstract Constant sub(Constant c)

Subtracts a value specified by another constant from this constant. Does not support adding value to a string constant. Automatic type upgrade will be done during the arithmetic.

Parameters:

c - constant whose value will be substracted from

Returns:

a constant with value equals to the value of this constant subtracted from that of another constant

mul

public abstract Constant mul(Constant c)

Multiplies this constant by a value specified by another constant. Does not support adding value to a string constant. Automatic type upgrade will be done during the arithmetic.

Parameters:

c - multiplier

Returns:

a constant with value equals to the value of this constant multiplied by that of another constant

div

public abstract Constant div(Constant c)

Divides this constant by a value specified by another constant. Does not support adding value to a string constant. Automatic type upgrade will be done during the arithmetic.

Parameters:

c - divider

Returns:

a constant with value equals to the value of this constant divided by that of another constant