TypeSafeDiagnosingMatcher (JUnit API)
Date: 2016-08-24

org.hamcrest

## Class TypeSafeDiagnosingMatcher<T>

- java.lang.Object
- - org.hamcrest.BaseMatcher<T>
  - - org.hamcrest.TypeSafeDiagnosingMatcher<T>

- Type Parameters:
    `T` -
  All Implemented Interfaces:
    Matcher<T>, SelfDescribing
  Direct Known Subclasses:
    CombinableMatcher, Every, FeatureMatcher, IsCollectionContaining

      public abstract class TypeSafeDiagnosingMatcher<T>
      extends BaseMatcher<T>

  Convenient base class for Matchers that require a non-null value of a specific type and that will report why the received value has been rejected. This implements the null check, checks the type and then casts. To use, implement

      matchesSafely()

  .

- - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `TypeSafeDiagnosingMatcher()` The default constructor for simple sub types
    `protected` | `TypeSafeDiagnosingMatcher(Class<?> expectedType)` Use this constructor if the subclass that implements `matchesSafely` is not the class that binds <T> to a type.
    `protected` | `TypeSafeDiagnosingMatcher(ReflectiveTypeFinder typeFinder)` Use this constructor if the subclass that implements `matchesSafely` is not the class that binds <T> to a type.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `describeMismatch(Object item, Description mismatchDescription)` Generate a description of why the matcher has not accepted the item.
    `boolean` | `matches(Object item)` Evaluates the matcher for argument item.
    `protected abstract boolean` | `matchesSafely(T item, Description mismatchDescription)` Subclasses should implement this.

    - ### Methods inherited from class org.hamcrest.BaseMatcher

      `_dont_implement_Matcher___instead_extend_BaseMatcher_, toString`

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

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

    - ### Methods inherited from interface org.hamcrest.SelfDescribing

      `describeTo`

- - ### Constructor Detail

    - #### TypeSafeDiagnosingMatcher

          protected TypeSafeDiagnosingMatcher(Class<?> expectedType)

      Use this constructor if the subclass that implements `matchesSafely` is not the class that binds <T> to a type.
      Parameters:
        `expectedType` - The expectedType of the actual value.

    - #### TypeSafeDiagnosingMatcher

          protected TypeSafeDiagnosingMatcher(ReflectiveTypeFinder typeFinder)

      Use this constructor if the subclass that implements `matchesSafely` is not the class that binds <T> to a type.
      Parameters:
        `typeFinder` - A type finder to extract the type

    - #### TypeSafeDiagnosingMatcher

          protected TypeSafeDiagnosingMatcher()

      The default constructor for simple sub types

  - ### Method Detail

    - #### matchesSafely

          protected abstract boolean matchesSafely(T item,
                                                   Description mismatchDescription)

      Subclasses should implement this. The item will already have been checked for the specific type and will never be null.

    - #### matches

          public final boolean matches(Object item)

      Description copied from interface: `Matcher`
      Evaluates the matcher for argument item.

      This method matches against Object, instead of the generic type T. This is because the caller of the Matcher does not know at runtime what the type is (because of type erasure with Java generics). It is down to the implementations to check the correct type.
      Parameters:
        `item` - the object against which the matcher is evaluated.
      Returns:
        `true` if item matches, otherwise `false`.
      See Also:
        `BaseMatcher`

    - #### describeMismatch

          public final void describeMismatch(Object item,
                                             Description mismatchDescription)

      Description copied from interface: `Matcher`
      Generate a description of why the matcher has not accepted the item. The description will be part of a larger description of why a matching failed, so it should be concise. This method assumes that `matches(item)` is false, but will not check this.
      Specified by:
        `describeMismatch` in interface `Matcher<T>`
      Overrides:
        `describeMismatch` in class `BaseMatcher<T>`
      Parameters:
        `item` - The item that the Matcher has rejected.
        `mismatchDescription` - The description to be built or appended to.