Package org.apache.commons.lang3.reflect

# Class TypeUtils

java.lang.Object
org.apache.commons.lang3.reflect.TypeUtils

public class TypeUtils extends Object
Utility methods focusing on type inspection, particularly with regard to generics.

Since:
  3.0

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static class`
  `TypeUtils.WildcardTypeBuilder`
  `WildcardType` builder.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final WildcardType`
  `WILDCARD_ALL`
  A wildcard instance matching `?`.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `TypeUtils()`
  `TypeUtils` instances should NOT be constructed in standard programming.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static boolean`
  `containsTypeVariables(Type type)`
  Tests, recursively, whether any of the type parameters associated with `type` are bound to variables.
  `static Map<TypeVariable<?>,Type>`
  `determineTypeArguments(Class<?> cls, ParameterizedType superParameterizedType)`
  Tries to determine the type arguments of a class/interface based on a super parameterized type's type arguments.
  `static boolean`
  `equals(Type type1, Type type2)`
  Tests equality of types.
  `static GenericArrayType`
  `genericArrayType(Type componentType)`
  Creates a generic array type instance.
  `static Type`
  `getArrayComponentType(Type type)`
  Gets the array component type of `type`.
  `static Type[]`
  `getImplicitBounds(TypeVariable<?> typeVariable)`
  Gets an array containing the sole type of `Object` if `TypeVariable.getBounds()` returns an empty array.
  `static Type[]`
  `getImplicitLowerBounds(WildcardType wildcardType)`
  Gets an array containing a single value of `null` if `WildcardType.getLowerBounds()` returns an empty array.
  `static Type[]`
  `getImplicitUpperBounds(WildcardType wildcardType)`
  Gets an array containing the sole value of `Object` if `WildcardType.getUpperBounds()` returns an empty array.
  `static Class<?>`
  `getRawType(Type type, Type assigningType)`
  Gets the raw type of a Java type, given its context.
  `static Map<TypeVariable<?>,Type>`
  `getTypeArguments(ParameterizedType type)`
  Gets all the type arguments for this parameterized type including owner hierarchy arguments such as `Outer<K, V>.Inner<T>.DeepInner<E>` .
  `static Map<TypeVariable<?>,Type>`
  `getTypeArguments(Type type, Class<?> toClass)`
  Gets the type arguments of a class/interface based on a subtype.
  `static boolean`
  `isArrayType(Type type)`
  Tests whether the specified type denotes an array type.
  `static boolean`
  `isAssignable(Type type, Type toType)`
  Tests if the subject type may be implicitly cast to the target type following the Java generics rules.
  `static boolean`
  `isInstance(Object value, Type type)`
  Tests if the given value can be assigned to the target type following the Java generics rules.
  `static Type[]`
  `normalizeUpperBounds(Type[] bounds)`
  Strips out the redundant upper bound types in type variable types and wildcard types (or it would with wildcard types if multiple upper bounds were allowed).
  `static final ParameterizedType`
  `parameterize(Class<?> rawClass, Type... typeArguments)`
  Creates a parameterized type instance.
  `static final ParameterizedType`
  `parameterize(Class<?> rawClass, Map<TypeVariable<?>,Type> typeVariableMap)`
  Creates a parameterized type instance.
  `static final ParameterizedType`
  `parameterizeWithOwner(Type owner, Class<?> rawClass, Type... typeArguments)`
  Creates a parameterized type instance.
  `static final ParameterizedType`
  `parameterizeWithOwner(Type owner, Class<?> rawClass, Map<TypeVariable<?>,Type> typeVariableMap)`
  Creates a parameterized type instance.
  `static String`
  `toLongString(TypeVariable<?> typeVariable)`
  Formats a `TypeVariable` including its `GenericDeclaration`.
  `static String`
  `toString(Type type)`
  Formats a given type as a Java-esque String.
  `static boolean`
  `typesSatisfyVariables(Map<TypeVariable<?>,Type> typeVariableMap)`
  Determines whether or not specified types satisfy the bounds of their mapped type variables.
  `static Type`
  `unrollVariables(Map<TypeVariable<?>,Type> typeArguments, Type type)`
  Gets a type representing `type` with variable assignments "unrolled."
  `static TypeUtils.WildcardTypeBuilder`
  `wildcardType()`
  Gets a `TypeUtils.WildcardTypeBuilder`.
  `static <T> Typed<T>`
  `wrap(Class<T> type)`
  Wraps the specified `Class` in a `Typed` wrapper.
  `static <T> Typed<T>`
  `wrap(Type type)`
  Wraps the specified `Type` in a `Typed` wrapper.

  ### Methods inherited from class java.lang.Object

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

- ## Field Details

  - ### WILDCARD_ALL

    public static final WildcardType WILDCARD_ALL
    A wildcard instance matching `?`.
    Since:
      3.2

- ## Constructor Details

  - ### TypeUtils

    public TypeUtils()
    `TypeUtils` instances should NOT be constructed in standard programming. Instead, the class should be used as `TypeUtils.isAssignable(cls, toClass)`.

    This constructor is public to permit tools that require a JavaBean instance to operate.

- ## Method Details

  - ### containsTypeVariables

    public static boolean containsTypeVariables(Type type)
    Tests, recursively, whether any of the type parameters associated with `type` are bound to variables.
    Parameters:
      `type` - the type to check for type variables
    Returns:
      boolean
    Since:
      3.2

  - ### determineTypeArguments

    public static Map<TypeVariable<?>,Type> determineTypeArguments(Class<?> cls, ParameterizedType superParameterizedType)
    Tries to determine the type arguments of a class/interface based on a super parameterized type's type arguments. This method is the inverse of `getTypeArguments(Type, Class)` which gets a class/interface's type arguments based on a subtype. It is far more limited in determining the type arguments for the subject class's type variables in that it can only determine those parameters that map from the subject `Class` object to the supertype.

    Example: `TreeSet` sets its parameter as the parameter for `NavigableSet`, which in turn sets the parameter of `SortedSet`, which in turn sets the parameter of `Set`, which in turn sets the parameter of `Collection`, which in turn sets the parameter of `Iterable`. Since `TreeSet`'s parameter maps (indirectly) to `Iterable`'s parameter, it will be able to determine that based on the super type `Iterable<? extends Map<Integer, ? extends Collection<?>>>`, the parameter of `TreeSet` is `? extends Map<Integer, ? extends Collection<?>>`.

    Parameters:
      `cls` - the class whose type parameters are to be determined, not `null`
      `superParameterizedType` - the super type from which `cls`'s type arguments are to be determined, not `null`
    Returns:
      a `Map` of the type assignments that could be determined for the type variables in each type in the inheritance hierarchy from `type` to `toClass` inclusive.
    Throws:
      `NullPointerException` - if either `cls` or `superParameterizedType` is `null`

  - ### equals

    public static boolean equals(Type type1, Type type2)
    Tests equality of types.
    Parameters:
      `type1` - the first type
      `type2` - the second type
    Returns:
      boolean
    Since:
      3.2

  - ### genericArrayType

    public static GenericArrayType genericArrayType(Type componentType)
    Creates a generic array type instance.
    Parameters:
      `componentType` - the type of the elements of the array. For example the component type of `boolean[]` is `boolean`
    Returns:
      `GenericArrayType`
    Since:
      3.2

  - ### getArrayComponentType

    public static Type getArrayComponentType(Type type)
    Gets the array component type of `type`.
    Parameters:
      `type` - the type to be checked
    Returns:
      component type or null if type is not an array type

  - ### getImplicitBounds

    public static Type[] getImplicitBounds(TypeVariable<?> typeVariable)
    Gets an array containing the sole type of `Object` if `TypeVariable.getBounds()` returns an empty array. Otherwise, it returns the result of `TypeVariable.getBounds()` passed into `normalizeUpperBounds(java.lang.reflect.Type[])`.
    Parameters:
      `typeVariable` - the subject type variable, not `null`
    Returns:
      a non-empty array containing the bounds of the type variable.
    Throws:
      `NullPointerException` - if `typeVariable` is `null`

  - ### getImplicitLowerBounds

    public static Type[] getImplicitLowerBounds(WildcardType wildcardType)
    Gets an array containing a single value of `null` if `WildcardType.getLowerBounds()` returns an empty array. Otherwise, it returns the result of `WildcardType.getLowerBounds()`.
    Parameters:
      `wildcardType` - the subject wildcard type, not `null`
    Returns:
      a non-empty array containing the lower bounds of the wildcard type.
    Throws:
      `NullPointerException` - if `wildcardType` is `null`

  - ### getImplicitUpperBounds

    public static Type[] getImplicitUpperBounds(WildcardType wildcardType)
    Gets an array containing the sole value of `Object` if `WildcardType.getUpperBounds()` returns an empty array. Otherwise, it returns the result of `WildcardType.getUpperBounds()` passed into `normalizeUpperBounds(java.lang.reflect.Type[])`.
    Parameters:
      `wildcardType` - the subject wildcard type, not `null`
    Returns:
      a non-empty array containing the upper bounds of the wildcard type.
    Throws:
      `NullPointerException` - if `wildcardType` is `null`

  - ### getRawType

    public static Class<?> getRawType(Type type, Type assigningType)
    Gets the raw type of a Java type, given its context. Primarily for use with `TypeVariable`s and `GenericArrayType`s, or when you do not know the runtime type of `type`: if you know you have a `Class` instance, it is already raw; if you know you have a `ParameterizedType`, its raw type is only a method call away.
    Parameters:
      `type` - to resolve
      `assigningType` - type to be resolved against
    Returns:
      the resolved `Class` object or `null` if the type could not be resolved

  - ### getTypeArguments

    public static Map<TypeVariable<?>,Type> getTypeArguments(ParameterizedType type)
    Gets all the type arguments for this parameterized type including owner hierarchy arguments such as `Outer<K, V>.Inner<T>.DeepInner<E>` . The arguments are returned in a `Map` specifying the argument type for each `TypeVariable`.
    Parameters:
      `type` - specifies the subject parameterized type from which to harvest the parameters.
    Returns:
      a `Map` of the type arguments to their respective type variables.

  - ### getTypeArguments

    public static Map<TypeVariable<?>,Type> getTypeArguments(Type type, Class<?> toClass)
    Gets the type arguments of a class/interface based on a subtype. For instance, this method will determine that both of the parameters for the interface `Map` are `Object` for the subtype `Properties` even though the subtype does not directly implement the `Map` interface.

    This method returns `null` if `type` is not assignable to `toClass`. It returns an empty map if none of the classes or interfaces in its inheritance hierarchy specify any type arguments.

    A side effect of this method is that it also retrieves the type arguments for the classes and interfaces that are part of the hierarchy between `type` and `toClass`. So with the above example, this method will also determine that the type arguments for `Hashtable` are also both `Object`. In cases where the interface specified by `toClass` is (indirectly) implemented more than once (e.g. where `toClass` specifies the interface `Iterable` and `type` specifies a parameterized type that implements both `Set` and `Collection`), this method will look at the inheritance hierarchy of only one of the implementations/subclasses; the first interface encountered that isn't a subinterface to one of the others in the `type` to `toClass` hierarchy.

    Parameters:
      `type` - the type from which to determine the type parameters of `toClass`
      `toClass` - the class whose type parameters are to be determined based on the subtype `type`
    Returns:
      a `Map` of the type assignments for the type variables in each type in the inheritance hierarchy from `type` to `toClass` inclusive.

  - ### isArrayType

    public static boolean isArrayType(Type type)
    Tests whether the specified type denotes an array type.
    Parameters:
      `type` - the type to be checked
    Returns:
      `true` if `type` is an array class or a `GenericArrayType`.

  - ### isAssignable

    public static boolean isAssignable(Type type, Type toType)
    Tests if the subject type may be implicitly cast to the target type following the Java generics rules. If both types are `Class` objects, the method returns the result of `ClassUtils.isAssignable(Class, Class)`.
    Parameters:
      `type` - the subject type to be assigned to the target type
      `toType` - the target type
    Returns:
      `true` if `type` is assignable to `toType`.

  - ### isInstance

    public static boolean isInstance(Object value, Type type)
    Tests if the given value can be assigned to the target type following the Java generics rules.
    Parameters:
      `value` - the value to be checked
      `type` - the target type
    Returns:
      `true` if `value` is an instance of `type`.

  - ### normalizeUpperBounds

    public static Type[] normalizeUpperBounds(Type[] bounds)
    Strips out the redundant upper bound types in type variable types and wildcard types (or it would with wildcard types if multiple upper bounds were allowed).

    Example, with the variable type declaration:

        <K extends java.util.Collection<String> &
         java.util.List<String>>

    since `List` is a subinterface of `Collection`, this method will return the bounds as if the declaration had been:

        <K extends java.util.List<String>>

    Parameters:
      `bounds` - an array of types representing the upper bounds of either `WildcardType` or `TypeVariable`, not `null`.
    Returns:
      an array containing the values from `bounds` minus the redundant types.
    Throws:
      `NullPointerException` - if `bounds` is `null`

  - ### parameterize

    public static final ParameterizedType parameterize(Class<?> rawClass, Map<TypeVariable<?>,Type> typeVariableMap)
    Creates a parameterized type instance.
    Parameters:
      `rawClass` - the raw class to create a parameterized type instance for
      `typeVariableMap` - the map used for parameterization
    Returns:
      `ParameterizedType`
    Throws:
      `NullPointerException` - if either `rawClass` or `typeVariableMap` is `null`
    Since:
      3.2

  - ### parameterize

    public static final ParameterizedType parameterize(Class<?> rawClass, Type... typeArguments)
    Creates a parameterized type instance.
    Parameters:
      `rawClass` - the raw class to create a parameterized type instance for
      `typeArguments` - the types used for parameterization
    Returns:
      `ParameterizedType`
    Throws:
      `NullPointerException` - if `rawClass` is `null`
    Since:
      3.2

  - ### parameterizeWithOwner

    public static final ParameterizedType parameterizeWithOwner(Type owner, Class<?> rawClass, Map<TypeVariable<?>,Type> typeVariableMap)
    Creates a parameterized type instance.
    Parameters:
      `owner` - the owning type
      `rawClass` - the raw class to create a parameterized type instance for
      `typeVariableMap` - the map used for parameterization
    Returns:
      `ParameterizedType`
    Throws:
      `NullPointerException` - if either `rawClass` or `typeVariableMap` is `null`
    Since:
      3.2

  - ### parameterizeWithOwner

    public static final ParameterizedType parameterizeWithOwner(Type owner, Class<?> rawClass, Type... typeArguments)
    Creates a parameterized type instance.
    Parameters:
      `owner` - the owning type
      `rawClass` - the raw class to create a parameterized type instance for
      `typeArguments` - the types used for parameterization
    Returns:
      `ParameterizedType`
    Throws:
      `NullPointerException` - if `rawClass` is `null`
    Since:
      3.2

  - ### toLongString

    public static String toLongString(TypeVariable<?> typeVariable)
    Formats a `TypeVariable` including its `GenericDeclaration`.
    Parameters:
      `typeVariable` - the type variable to create a String representation for, not `null`
    Returns:
      String
    Throws:
      `NullPointerException` - if `typeVariable` is `null`
    Since:
      3.2

  - ### toString

    public static String toString(Type type)
    Formats a given type as a Java-esque String.
    Parameters:
      `type` - the type to create a String representation for, not `null`
    Returns:
      String
    Throws:
      `NullPointerException` - if `type` is `null`
    Since:
      3.2

  - ### typesSatisfyVariables

    public static boolean typesSatisfyVariables(Map<TypeVariable<?>,Type> typeVariableMap)
    Determines whether or not specified types satisfy the bounds of their mapped type variables. When a type parameter extends another (such as `<T, S extends T>`), uses another as a type parameter (such as `<T, S extends Comparable>>`), or otherwise depends on another type variable to be specified, the dependencies must be included in `typeVarAssigns`.
    Parameters:
      `typeVariableMap` - specifies the potential types to be assigned to the type variables, not `null`.
    Returns:
      whether or not the types can be assigned to their respective type variables.
    Throws:
      `NullPointerException` - if `typeVariableMap` is `null`

  - ### unrollVariables

    public static Type unrollVariables(Map<TypeVariable<?>,Type> typeArguments, Type type)
    Gets a type representing `type` with variable assignments "unrolled."
    Parameters:
      `typeArguments` - as from `getTypeArguments(Type, Class)`
      `type` - the type to unroll variable assignments for
    Returns:
      Type
    Since:
      3.2

  - ### wildcardType

    public static TypeUtils.WildcardTypeBuilder wildcardType()
    Gets a `TypeUtils.WildcardTypeBuilder`.
    Returns:
      `TypeUtils.WildcardTypeBuilder`
    Since:
      3.2

  - ### wrap

    public static <T> Typed<T> wrap(Class<T> type)
    Wraps the specified `Class` in a `Typed` wrapper.
    Type Parameters:
      `T` - generic type
    Parameters:
      `type` - to wrap
    Returns:
      Typed<T>
    Since:
      3.2

  - ### wrap

    public static <T> Typed<T> wrap(Type type)
    Wraps the specified `Type` in a `Typed` wrapper.
    Type Parameters:
      `T` - inferred generic type
    Parameters:
      `type` - to wrap
    Returns:
      Typed<T>
    Since:
      3.2