Apache Commons Lang 3.20.0 · org.apache.commons.lang3.reflect.TypeLiteral

Type literal comparable to javax.enterprise.util.TypeLiteral, made generally available outside the JEE context. Allows the passing around of a "token" that represents a type in a typesafe manner, as opposed to passing the (non-parameterized) Type object itself. Consider:

You might see such a typesafe API as:

class Typesafe {
  <T> T obtain(Class<T> type, ...);
}

Consumed in the manner of:

Foo foo = typesafe.obtain(Foo.class, ...);

Yet, you run into problems when you want to do this with a parameterized type:

List<String> listOfString = typesafe.obtain(List.class, ...); // could only give us a raw List

java.lang.reflect.Type might provide some value:

Type listOfStringType = ...; // firstly, how to obtain this? Doable, but not straightforward.
List<String> listOfString = (List<String>) typesafe.obtain(listOfStringType, ...); // nongeneric Type would necessitate a cast

The "type literal" concept was introduced to provide an alternative, i.e.:

class Typesafe {
  <T> T obtain(TypeLiteral<T> type, ...);
}

Consuming code looks like:

List<String> listOfString = typesafe.obtain(new TypeLiteral<List<String>>() {}, ...);

This has the effect of "jumping up" a level to tie a java.lang.reflect.Type to a type variable while simultaneously making it short work to obtain a Type instance for any given type, inline.

Additionally TypeLiteral implements the Typed interface which is a generalization of this concept, and which may be implemented in custom classes. It is suggested that APIs be defined in terms of the interface, in the following manner:

<T> T obtain(Typed<T> typed, ...);

Modifier and Type	Field and Description
private static final TypeVariable<Class<TypeLiteral<T>>>	T
private final String	toString
public final Type	value Represented type.

Access	Constructor and Description
protected	TypeLiteral() Constructs a new instance.

Modifier and Type	Method and Description
public final boolean	equals(final Object obj) Overrides java.lang.Object.equals. Indicates whether some other object is "equal to" this one.
public Type	getType() Implements org.apache.commons.lang3.reflect.Typed.getType. Gets the `Type` represented by this entity.
public int	hashCode() Overrides java.lang.Object.hashCode. Returns a hash code value for this object.
public String	toString() Overrides java.lang.Object.toString. Returns a string representation of the object.

T	back to summary
private static final TypeVariable<Class<TypeLiteral<T>>> T Annotations @SuppressWarnings:rawtypes

toString	back to summary
private final String toString

value	back to summary
public final Type value Represented type.

TypeLiteral	back to summary
protected TypeLiteral() Constructs a new instance.

Method Detail

equals back to summary

equals	back to summary
public final boolean equals(final Object obj) Overrides java.lang.Object.equals. Doc from java.lang.Object.equals. Indicates whether some other object is "equal to" this one. The `equals` method implements an equivalence relation on non-null object references: It is reflexive: for any non-null reference value `x`, `x.equals(x)` should return `true`. It is symmetric: for any non-null reference values `x` and `y`, `x.equals(y)` should return `true` if and only if `y.equals(x)` returns `true`. It is transitive: for any non-null reference values `x`, `y`, and `z`, if `x.equals(y)` returns `true` and `y.equals(z)` returns `true`, then `x.equals(z)` should return `true`. It is consistent: for any non-null reference values `x` and `y`, multiple invocations of `x.equals(y)` consistently return `true` or consistently return `false`, provided no information used in `equals` comparisons on the objects is modified. For any non-null reference value `x`, `x.equals(null)` should return `false`. An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes. Annotations @Override

public final boolean equals(final Object obj)

Overrides java.lang.Object.equals.

Doc from java.lang.Object.equals.

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

It is reflexive: for any non-null reference value x, x.equals(x) should return true.
It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
For any non-null reference value x, x.equals(null) should return false.

An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

Annotations

@Override

getType back to summary

getType	back to summary
public Type getType() Implements org.apache.commons.lang3.reflect.Typed.getType. Doc from org.apache.commons.lang3.reflect.Typed.getType. Gets the `Type` represented by this entity. Annotations @Override

public Type getType()

Implements org.apache.commons.lang3.reflect.Typed.getType.

Doc from org.apache.commons.lang3.reflect.Typed.getType.

Gets the Type represented by this entity.

Annotations

@Override

hashCode back to summary

hashCode	back to summary
public int hashCode() Overrides java.lang.Object.hashCode. Doc from java.lang.Object.hashCode. Returns a hash code value for this object. This method is supported for the benefit of hash tables such as those provided by `java.util.HashMap`. The general contract of `hashCode` is: Whenever it is invoked on the same object more than once during an execution of a Java application, the `hashCode` method must consistently return the same integer, provided no information used in `equals` comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application. If two objects are equal according to the `equals` method, then calling the `hashCode` method on each of the two objects must produce the same integer result. It is not required that if two objects are unequal according to the `equals` method, then calling the `hashCode` method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables. Annotations @Override

public int hashCode()

Overrides java.lang.Object.hashCode.

Doc from java.lang.Object.hashCode.

Returns a hash code value for this object. This method is supported for the benefit of hash tables such as those provided by java.util.HashMap.

The general contract of hashCode is:

Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
If two objects are equal according to the equals method, then calling the hashCode method on each of the two objects must produce the same integer result.
It is not required that if two objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

Annotations

@Override

toString back to summary

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Doc from java.lang.Object.toString. Returns a string representation of the object. Satisfying this method's contract implies a non-`null` result must be returned. Annotations @Override

public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object. Satisfying this method's contract implies a non-null result must be returned.

Annotations

@Override

public abstract Class TypeLiteral<T>

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail