Enum Class Nullness

java.lang.Object

java.lang.Enum<Nullness>

com.google.errorprone.dataflow.nullnesspropagation.Nullness

All Implemented Interfaces:

Serializable, Comparable<Nullness>, Constable, org.checkerframework.errorprone.dataflow.analysis.AbstractValue<Nullness>

public enum Nullness
extends Enum<Nullness>
implements org.checkerframework.errorprone.dataflow.analysis.AbstractValue<Nullness>

Represents one of the possible nullness values in our nullness analysis.

Author:

deminguyen@google.com (Demi Nguyen)

Nested Class Summary

Nested classes/interfaces inherited from class Enum

Enum.EnumDesc<E>

Enum Constant Summary

Enum Constants

Enum Constant	Description
BOTTOM
NONNULL
NULL
NULLABLE	The lattice for nullness looks like:

Method Summary

Modifier and Type	Method	Description
Nullness	deducedValueWhenNotEqual()	Returns the Nullness that corresponds to what you can deduce by knowing that some expression is not equal to another expression with this Nullness.
Nullness	greatestLowerBound(Nullness other)
Nullness	leastUpperBound(Nullness other)
String	toString()
static Nullness	valueOf(String name)	Returns the enum constant of this class with the specified name.
static Nullness[]	values()	Returns an array containing the constants of this enum class, in the order they are declared.

Methods inherited from class Enum

clone, compareTo, describeConstable, equals, finalize, getDeclaringClass, hashCode, name, ordinal, valueOf

Methods inherited from class Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Details

NULLABLE

public static final Nullness NULLABLE

The lattice for nullness looks like:

       Nullable
      /        \
  Null          Non-null
       \      /
        Bottom

NULL

public static final Nullness NULL

NONNULL

public static final Nullness NONNULL

BOTTOM

public static final Nullness BOTTOM

Method Details

values

public static Nullness[] values()

Returns an array containing the constants of this enum class, in the order they are declared.

Returns:

an array containing the constants of this enum class, in the order they are declared

valueOf

public static Nullness valueOf(String name)

Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum class has no constant with the specified name

NullPointerException - if the argument is null

leastUpperBound

public Nullness leastUpperBound(Nullness other)

Specified by:

leastUpperBound in interface org.checkerframework.errorprone.dataflow.analysis.AbstractValue<Nullness>

greatestLowerBound

public Nullness greatestLowerBound(Nullness other)

deducedValueWhenNotEqual

public Nullness deducedValueWhenNotEqual()

Returns the Nullness that corresponds to what you can deduce by knowing that some expression is not equal to another expression with this Nullness.

A Nullness represents a set of possible values for a expression. Suppose you have two variables var1 and var2. If var1 != var2, then var1 must be an element of the complement of the singleton set containing the value of var2. If you union these complement sets over all possible values of var2, the set that results is what this method returns, assuming that this is the Nullness of var2.

Example 1: Suppose nv2 == NULL. Then var2 can have exactly one value, null, and var1 must have a value in the set of all values except null. That set is exactly NONNULL.

Example 2: Suppose nv2 == NONNULL. Then var2 can have any value except null. Suppose var2 has value "foo". Then var1 must have a value in the set of all values except "foo". Now suppose var2 has value "bar" . Then var1 must have a value in set of all values except "bar". Since we don't know which value in the set NONNULL var2 has, we union all possible complement sets to get the set of all values, or NULLABLE.

toString

public String toString()

Overrides:

toString in class Enum<Nullness>