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Restore ListUtils map methods that accept UnaryOperator (#4729)
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* Restore ListUtils map methods that accept UnaryOperator

Following #4720

* Remove deprecated annotations as folks are not expected to cast their args
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@timtebeek
timtebeek authored Nov 28, 2024
1 parent a40fbb5 commit 7f43cc1
Showing 1 changed file with 54 additions and 31 deletions.
85 changes: 54 additions & 31 deletions rewrite-core/src/main/java/org/openrewrite/internal/ListUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@
import java.util.List;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.UnaryOperator;

import static java.util.Collections.emptyList;
import static java.util.Collections.singletonList;
Expand All @@ -33,6 +34,7 @@
* <p>
* If the transformation does not involve modifying LST elements or broader set of stream operations
* is needed, the Java Streams API may be more suitable.
*
* @implNote Most transformation methods in this class accept endomorphic mapping functions, i.e., functions
* of the form {@code f: T -> T}. The primary goal of these methods is to produce minimal change in a list’s structure,
* ensuring unnecessary memory allocations are avoided,
Expand Down Expand Up @@ -89,10 +91,10 @@ public static <T> List<T> insertInOrder(@Nullable List<T> ls, T insert, Comparat
* Insert element to a list at the specified position in the list.
* Throws the same exceptions as List.add()
*
* @param ls The original list.
* @param t The element to add.
* @param ls The original list.
* @param t The element to add.
* @param index index at which the specified element is to be inserted
* @param <T> The type of elements in the list.
* @param <T> The type of elements in the list.
* @return A new list with the element inserted at the specified position.
*/
public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index) {
Expand All @@ -103,7 +105,7 @@ public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index)
return ls;
}

List<T> newLs = ls == null ? new ArrayList<>(1) : new ArrayList<>(ls);
List<T> newLs = ls == null ? new ArrayList<>(1) : new ArrayList<>(ls);
newLs.add(index, t);
return newLs;
}
Expand All @@ -112,9 +114,9 @@ public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index)
* Applies the specified mapping function to the last element of the list.
* If the resulting element is null, the last element is removed from the list.
*
* @param ls The list to modify.
* @param mapLast The mapping function to apply to the last element.
* @param <T> The type of elements in the list.
* @param ls The list to modify.
* @param mapLast The mapping function to apply to the last element.
* @param <T> The type of elements in the list.
* @return A new list with the modified last element, or the original list if unchanged.
*/
@Contract("null, _ -> null; !null, _ -> !null")
Expand All @@ -137,6 +139,13 @@ public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index)
return ls;
}

/**
* For backwards compatibility; prefer {@link #mapLast(List, Function)}.
*/
public static <T> @Nullable List<T> mapLast(@Nullable List<T> ls, UnaryOperator<@Nullable T> mapLast) {
return mapLast(ls, (Function<T, T>) mapLast);
}

/**
* Applies the specified mapping function to the first element of the list.
* If the resulting element is null, the first element is removed from the list.
Expand Down Expand Up @@ -166,13 +175,20 @@ public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index)
return ls;
}

/**
* For backwards compatibility; prefer {@link #mapFirst(List, Function)}.
*/
public static <T> @Nullable List<T> mapFirst(@Nullable List<T> ls, UnaryOperator<@Nullable T> mapFirst) {
return mapFirst(ls, (Function<T, T>) mapFirst);
}

/**
* Applies a mapping function to each element in the list along with its index.
* If any mapped element is null, it will be removed from the resulting list.
*
* @param ls The list to modify.
* @param map The mapping function that takes an index and an element.
* @param <T> The type of elements in the list.
* @param ls The list to modify.
* @param map The mapping function that takes an index and an element.
* @param <T> The type of elements in the list.
* @return A new list with modified elements, or the original list if unchanged.
*/
@Contract("null, _ -> null; !null, _ -> !null")
Expand Down Expand Up @@ -207,9 +223,9 @@ public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index)
/**
* Applies a mapping function to each element in the list. If any mapped element is null, it will be removed.
*
* @param ls The list to modify.
* @param map The mapping function to apply to each element.
* @param <T> The type of elements in the list.
* @param ls The list to modify.
* @param map The mapping function to apply to each element.
* @param <T> The type of elements in the list.
* @return A new list with modified elements, or the original list if unchanged.
*/
// inlined version of `map(List, BiFunction)` for memory efficiency (no overhead for lambda)
Expand Down Expand Up @@ -242,14 +258,21 @@ public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index)
return newLs;
}

/**
* For backwards compatibility; prefer {@link #map(List, Function)}.
*/
public static <T> @Nullable List<T> map(@Nullable List<T> ls, UnaryOperator<@Nullable T> map) {
return map(ls, (Function<T, T>) map);
}

/**
* Applies a flat-mapping function to each element in the list with its index.
* Each element may map to a single object or an iterable of objects.
* If any mapped element is null, it will be removed from the list.
*
* @param ls The list to modify.
* @param flatMap The flat-mapping function that takes an index and an element.
* @param <T> The type of elements in the list.
* @param ls The list to modify.
* @param flatMap The flat-mapping function that takes an index and an element.
* @param <T> The type of elements in the list.
* @return A new list with expanded or modified elements, or the original list if unchanged.
*/
@Contract("null, _ -> null; !null, _ -> !null")
Expand Down Expand Up @@ -319,9 +342,9 @@ public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index)
/**
* Applies a flat-mapping function to each element in the list. Each element may map to a single object or an iterable.
*
* @param ls The list to modify.
* @param flatMap The flat-mapping function to apply to each element.
* @param <T> The type of elements in the list.
* @param ls The list to modify.
* @param flatMap The flat-mapping function to apply to each element.
* @param <T> The type of elements in the list.
* @return A new list with expanded or modified elements, or the original list if unchanged.
*/
@Contract("null, _ -> null; !null, _ -> !null")
Expand All @@ -332,9 +355,9 @@ public static <T> List<T> insert(@Nullable List<T> ls, @Nullable T t, int index)
/**
* Concatenates a single element to the end of the list. If the element is null, returns the original list.
*
* @param ls The original list.
* @param t The element to concatenate.
* @param <T> The type of elements in the list.
* @param ls The original list.
* @param t The element to concatenate.
* @param <T> The type of elements in the list.
* @return A new list with the added element, or an empty list if the element or list is null.
*/
public static <T> List<T> concat(@Nullable List<T> ls, @Nullable T t) {
Expand All @@ -352,9 +375,9 @@ public static <T> List<T> concat(@Nullable List<T> ls, @Nullable T t) {
/**
* Concatenates a single element to the beginning of the list. If the element is null, returns the original list.
*
* @param t The element to add.
* @param ls The original list.
* @param <T> The type of elements in the list.
* @param t The element to add.
* @param ls The original list.
* @param <T> The type of elements in the list.
* @return A new list with the added element at the start, the original list if the element is null or a null
* object if both element and list are null.
*/
Expand All @@ -377,9 +400,9 @@ public static <T> List<T> concat(@Nullable List<T> ls, @Nullable T t) {
/**
* Concatenates two lists. If both are null, returns null. If only one is null, returns the other.
*
* @param ls The original list.
* @param t The list to concatenate.
* @param <T> The type of elements in the lists.
* @param ls The original list.
* @param t The list to concatenate.
* @param <T> The type of elements in the lists.
* @return A new list containing both lists, or one of the lists if the other is null.
*/
@Contract("null, null -> null; !null, _ -> !null; _, !null -> !null")
Expand Down Expand Up @@ -427,8 +450,8 @@ public static <T> List<T> insertAll(@Nullable List<T> ls, int index, @Nullable L
/**
* Returns null if the list is empty; otherwise, returns the list.
*
* @param ls The list to check.
* @param <T> The type of elements in the list.
* @param ls The list to check.
* @param <T> The type of elements in the list.
* @return Null if the list is empty; otherwise, the list.
*/
public static <T> @Nullable List<T> nullIfEmpty(@Nullable List<T> ls) {
Expand All @@ -454,7 +477,7 @@ public static <T> List<T> insertAll(@Nullable List<T> ls, int index, @Nullable L
* Returns null if the array is empty; otherwise, returns the array.
*
* @param array The array to check.
* @param <T> The type of elements in the array.
* @param <T> The type of elements in the array.
* @return Null if the array is empty; otherwise, the array.
*/
public static <T> T @Nullable [] nullIfEmpty(T @Nullable [] array) {
Expand Down

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