Applying my patch from LANG-469 - adding a lastOrdinalIndexOf method to complement the existing ordinalIndexOf method

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@891142 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/lang3/StringUtils.java

@@ -831,6 +831,12 @@ public class StringUtils {
      * StringUtils.ordinalIndexOf("aabaabaa", "", 2)   = 0
      * </pre>
      *
+     * <p>Note that 'head(String str, int n)' may be implemented as: </p>
+     *
+     * <pre>
+     *   str.substring(0, lastOrdinalIndexOf(str, "\n", n))
+     * </pre>
+     *
      * @param str  the String to check, may be null
      * @param searchStr  the String to find, may be null
      * @param ordinal  the n-th <code>searchStr</code> to find
@@ -839,16 +845,25 @@ public class StringUtils {
      * @since 2.1
      */
     public static int ordinalIndexOf(String str, String searchStr, int ordinal) {
+        return ordinalIndexOf(str, searchStr, ordinal, false);
+    }
+
+    // Shared code between ordinalIndexOf(String,String,int) and lastOrdinalIndexOf(String,String,int)
+    private static int ordinalIndexOf(String str, String searchStr, int ordinal, boolean lastIndex) {
         if (str == null || searchStr == null || ordinal <= 0) {
             return INDEX_NOT_FOUND;
         }
         if (searchStr.length() == 0) {
-            return 0;
+            return lastIndex ? str.length() : 0;
         }
         int found = 0;
-        int index = INDEX_NOT_FOUND;
+        int index = lastIndex ? str.length() : INDEX_NOT_FOUND;
         do {
-            index = str.indexOf(searchStr, index + 1);
+            if(lastIndex) {
+                index = str.lastIndexOf(searchStr, index - 1);
+            } else {
+                index = str.indexOf(searchStr, index + 1);
+            }
             if (index < 0) {
                 return index;
             }
@@ -990,6 +1005,43 @@ public class StringUtils {
         return str.lastIndexOf(searchStr);
     }
 
+    /**
+     * <p>Finds the n-th last index within a String, handling <code>null</code>.
+     * This method uses {@link String#lastIndexOf(String)}.</p>
+     *
+     * <p>A <code>null</code> String will return <code>-1</code>.</p>
+     *
+     * <pre>
+     * StringUtils.lastOrdinalIndexOf(null, *, *)          = -1
+     * StringUtils.lastOrdinalIndexOf(*, null, *)          = -1
+     * StringUtils.lastOrdinalIndexOf("", "", *)           = 0
+     * StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 1)  = 7
+     * StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 2)  = 6
+     * StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 1)  = 5
+     * StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 2)  = 2
+     * StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 1) = 4
+     * StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 2) = 1
+     * StringUtils.lastOrdinalIndexOf("aabaabaa", "", 1)   = 8
+     * StringUtils.lastOrdinalIndexOf("aabaabaa", "", 2)   = 8
+     * </pre>
+     *
+     * <p>Note that 'tail(String str, int n)' may be implemented as: </p>
+     *
+     * <pre>
+     *   str.substring(lastOrdinalIndexOf(str, "\n", n) + 1)
+     * </pre>
+     *
+     * @param str  the String to check, may be null
+     * @param searchStr  the String to find, may be null
+     * @param ordinal  the n-th last <code>searchStr</code> to find
+     * @return the n-th last index of the search String,
+     *  <code>-1</code> (<code>INDEX_NOT_FOUND</code>) if no match or <code>null</code> string input
+     * @since 3.0
+     */
+    public static int lastOrdinalIndexOf(String str, String searchStr, int ordinal) {
+        return ordinalIndexOf(str, searchStr, ordinal, true);
+    }
+
     /**
      * <p>Finds the first index within a String, handling <code>null</code>.
      * This method uses {@link String#lastIndexOf(String, int)}.</p>
@@ -5836,5 +5888,4 @@ public class StringUtils {
         int strOffset = str.length() - suffix.length();
         return str.regionMatches(ignoreCase, strOffset, suffix, 0, suffix.length());
     }
-
 }

src/test/org/apache/commons/lang3/StringUtilsEqualsIndexOfTest.java

@@ -230,6 +230,20 @@ public class StringUtilsEqualsIndexOfTest extends TestCase {
         assertEquals(4, StringUtils.lastIndexOf("aabaabaa", "ab"));
     }
 
+    public void testLastOrdinalIndexOf() {
+        assertEquals(-1, StringUtils.lastOrdinalIndexOf(null, "*", 42) );
+        assertEquals(-1, StringUtils.lastOrdinalIndexOf("*", null, 42) );
+        assertEquals(0, StringUtils.lastOrdinalIndexOf("", "", 42) );
+        assertEquals(7, StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 1) );
+        assertEquals(6, StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 2) );
+        assertEquals(5, StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 1) );
+        assertEquals(2, StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 2) );
+        assertEquals(4, StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 1) );
+        assertEquals(1, StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 2) );
+        assertEquals(8, StringUtils.lastOrdinalIndexOf("aabaabaa", "", 1) );
+        assertEquals(8, StringUtils.lastOrdinalIndexOf("aabaabaa", "", 2) );
+    }
+
     public void testLastIndexOf_StringInt() {
         assertEquals(-1, StringUtils.lastIndexOf(null, null, 0));
         assertEquals(-1, StringUtils.lastIndexOf(null, null, -1));