kvr000 commented on code in PR #1270:
URL: https://github.com/apache/commons-lang/pull/1270#discussion_r1742875196
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src/main/java/org/apache/commons/lang3/SortedListUtils.java:
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@@ -0,0 +1,89 @@
+package org.apache.commons.lang3;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.function.Function;
+
+
+/**
+ * Operations on sorted {@link List}.
+ *
+ * @author Zbynek Vyskovsky
+ */
+public class SortedListUtils {
+ /**
+ * Finds element in sorted list.
+ *
+ * @param a
+ * list sorted by key field
+ * @param key
+ * key to search for
+ * @param keyExtractor
+ * function to extract key from element
+ * @param c
+ * comparator for keys
+ *
+ * @return
+ * index of the search key, if it is contained in the array within
the specified range; otherwise, (-(insertion
+ * point) - 1). The insertion point is defined as the point at which
the key would be inserted into the array:
+ * the index of the first element in the range greater than the key,
or toIndex if all elements in the range
+ * are less than the specified key. Note that this guarantees that
the return value will be >= 0 if and only if
+ * the key is found.
+ *
+ * @param <T>
+ * type of array element
+ * @param <K>
+ * type of key
+ */
+ public static <K, T> int binarySearch(List<T> a, K key,
+ Function<T, K> keyExtractor,
Comparator<? super K> c) {
+ return binarySearch(a, 0, a.size(), key, keyExtractor, c);
+ }
+
+ /**
+ * Finds element in sorted list, within range fromIndex - toIndex
(inclusive - exclusive).
+ *
+ * @param a
+ * list sorted by key field
+ * @param fromIndex
+ * start index
+ * @param toIndex
+ * end index (exclusive)
+ * @param key
+ * key to search for
+ * @param keyExtractor
+ * function to extract key from element
+ * @param c
+ * comparator for keys
+ *
+ * @return
+ * index of the search key, if it is contained in the array within
the specified range; otherwise, (-(insertion
+ * point) - 1). The insertion point is defined as the point at which
the key would be inserted into the array:
+ * the index of the first element in the range greater than the key,
or toIndex if all elements in the range
+ * are less than the specified key. Note that this guarantees that
the return value will be >= 0 if and only if
+ * the key is found.
+ *
+ * @param <T>
+ * type of array element
+ * @param <K>
+ * type of key
+ */
+ public static <T, K> int binarySearch(List<T> a, int fromIndex, int
toIndex, K key,
Review Comment:
Well, the `binarySearch()` is so common that everybody writes it the same
way as we learnt in school 😁. I do understand your comment though.
I wrote the code with different names of variables, added explaining
comments and different calculation of not-found result. There is little to do
about the algorithm itself but the same algorithms appear everywhere, including
Wiki, so Oracle definitely cannot claim license on this.
Hope this helps.
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