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#100 Introduce ClassUtils#tryCast
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2 files changed

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Diff for: ‎src/main/java/ch/jalu/typeresolver/classutil/ClassUtils.java

+17
Original file line numberDiff line numberDiff line change
@@ -59,6 +59,23 @@ public static Class<?> loadClassOrThrow(String name) {
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}
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}
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/**
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* Returns an optional with the given object cast to the target type, or an empty optional if the given object
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* cannot be cast to the specified type.
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*
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* @param object the object to cast
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* @param targetType the class to cast to
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* @param <T> target type
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* @return optional with the cast object, or empty optional if not possible
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*/
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@SuppressWarnings("unchecked")
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public static <T> Optional<T> tryCast(@Nullable Object object, Class<T> targetType) {
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if (targetType.isInstance(object)) {
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return Optional.of((T) object);
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}
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return Optional.empty();
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}
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/**
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* Returns an Optional with the same class cast as subtype of the given {@code parent} if possible,
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* otherwise returns an empty optional.

Diff for: ‎src/test/java/ch/jalu/typeresolver/classutil/ClassUtilsTest.java

+57-26
Original file line numberDiff line numberDiff line change
@@ -98,34 +98,65 @@ void shouldLoadClassOrThrowException() {
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}
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}
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@Test
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void shouldCastClassAsSubclass() {
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// given / when
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Optional<Class<? extends CharSequence>> result1 = ClassUtils.asSubclassIfPossible(String.class, CharSequence.class);
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Optional<Class<? extends Number>> result2 = ClassUtils.asSubclassIfPossible(Integer.class, Number.class);
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Optional<Class<? extends Serializable>> result3 = ClassUtils.asSubclassIfPossible(Integer.class, Serializable.class);
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Optional<Class<? extends Number[]>> result4 = ClassUtils.asSubclassIfPossible(Integer[].class, Number[].class);
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Optional<Class<? extends Double>> result5 = ClassUtils.asSubclassIfPossible(Double.class, Double.class);
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Optional<Class<? extends Integer>> result6 = ClassUtils.asSubclassIfPossible(int.class, int.class);
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// then
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assertThat(result1, equalTo(Optional.of(String.class)));
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assertThat(result2, equalTo(Optional.of(Integer.class)));
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assertThat(result3, equalTo(Optional.of(Integer.class)));
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assertThat(result4, equalTo(Optional.of(Integer[].class)));
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assertThat(result5, equalTo(Optional.of(Double.class)));
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assertThat(result6, equalTo(Optional.of(int.class)));
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}
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@Nested
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class SubClassAndCastingUtils {
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@Test
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void shouldNotCastAsSubclassWhenNotPossible() {
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// given / when / then
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assertThat(ClassUtils.asSubclassIfPossible(String.class, Number.class), equalTo(Optional.empty()));
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assertThat(ClassUtils.asSubclassIfPossible(Number.class, Integer.class), equalTo(Optional.empty()));
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assertThat(ClassUtils.asSubclassIfPossible(Integer[].class, CharSequence[].class), equalTo(Optional.empty()));
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@Test
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void shouldCastToTargetType() {
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// given / when
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Optional<Number> result1 = ClassUtils.tryCast(3, Number.class);
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Optional<String> result2 = ClassUtils.tryCast("str", String.class);
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Optional<Serializable> result3 = ClassUtils.tryCast("str", Serializable.class);
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Integer[] integerArray = {1, 2, 3};
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Optional<Number[]> result4 = ClassUtils.tryCast(integerArray, Number[].class);
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// then
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assertThat(result1, equalTo(Optional.of(3)));
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assertThat(result2, equalTo(Optional.of("str")));
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assertThat(result3, equalTo(Optional.of("str")));
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assertThat(result4, equalTo(Optional.of(integerArray)));
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}
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@Test
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void shouldNotCastObjectWhenNotPossible() {
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// given / when / then
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assertThat(ClassUtils.tryCast(3, String.class), equalTo(Optional.empty()));
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assertThat(ClassUtils.tryCast("str", Character[].class), equalTo(Optional.empty()));
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assertThat(ClassUtils.tryCast(null, Number.class), equalTo(Optional.empty()));
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assertThat(ClassUtils.asSubclassIfPossible(int.class, Integer.class), equalTo(Optional.empty()));
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assertThat(ClassUtils.asSubclassIfPossible(Integer.class, int.class), equalTo(Optional.empty()));
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// Special case Integer <-> int: Integer is not considered an int.class
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assertThat(ClassUtils.tryCast(3, int.class), equalTo(Optional.empty()));
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}
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@Test
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void shouldCastClassAsSubclass() {
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// given / when
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Optional<Class<? extends CharSequence>> result1 = ClassUtils.asSubclassIfPossible(String.class, CharSequence.class);
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Optional<Class<? extends Number>> result2 = ClassUtils.asSubclassIfPossible(Integer.class, Number.class);
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Optional<Class<? extends Serializable>> result3 = ClassUtils.asSubclassIfPossible(Integer.class, Serializable.class);
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Optional<Class<? extends Number[]>> result4 = ClassUtils.asSubclassIfPossible(Integer[].class, Number[].class);
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Optional<Class<? extends Double>> result5 = ClassUtils.asSubclassIfPossible(Double.class, Double.class);
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Optional<Class<? extends Integer>> result6 = ClassUtils.asSubclassIfPossible(int.class, int.class);
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// then
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assertThat(result1, equalTo(Optional.of(String.class)));
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assertThat(result2, equalTo(Optional.of(Integer.class)));
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assertThat(result3, equalTo(Optional.of(Integer.class)));
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assertThat(result4, equalTo(Optional.of(Integer[].class)));
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assertThat(result5, equalTo(Optional.of(Double.class)));
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assertThat(result6, equalTo(Optional.of(int.class)));
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}
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@Test
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void shouldNotCastAsSubclassWhenNotPossible() {
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// given / when / then
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assertThat(ClassUtils.asSubclassIfPossible(String.class, Number.class), equalTo(Optional.empty()));
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assertThat(ClassUtils.asSubclassIfPossible(Number.class, Integer.class), equalTo(Optional.empty()));
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assertThat(ClassUtils.asSubclassIfPossible(Integer[].class, CharSequence[].class), equalTo(Optional.empty()));
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assertThat(ClassUtils.asSubclassIfPossible(int.class, Integer.class), equalTo(Optional.empty()));
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assertThat(ClassUtils.asSubclassIfPossible(Integer.class, int.class), equalTo(Optional.empty()));
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}
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}
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@Test

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