8028321: Fix for String.split() empty input sequence/JDK-6559590 triggers regression

Summary: to undo the change for 6559590
Reviewed-by: darcy

src/share/classes/java/lang/String.java

@@ -2235,8 +2235,7 @@ public final class String
      * expression or is terminated by the end of the string.  The substrings in
      * the array are in the order in which they occur in this string.  If the
      * expression does not match any part of the input then the resulting array
-     * has just one element, namely this string. A zero-length input sequence
-     * always results zero-length resulting array.
+     * has just one element, namely this string.
      *
      * <p> When there is a positive-width match at the beginning of this
      * string then an empty leading substring is included at the beginning
@@ -2331,8 +2330,6 @@ public final class String
             (ch < Character.MIN_HIGH_SURROGATE ||
              ch > Character.MAX_LOW_SURROGATE))
         {
-            if (value.length == 0)
-                return new String[0];
             int off = 0;
             int next = 0;
             boolean limited = limit > 0;

src/share/classes/java/util/regex/Pattern.java

@@ -1144,8 +1144,7 @@ public final class Pattern
      * substrings in the array are in the order in which they occur in the
      * input. If this pattern does not match any subsequence of the input then
      * the resulting array has just one element, namely the input sequence in
-     * string form. A zero-length input sequence always results zero-length
-     * resulting array.
+     * string form.
      *
      * <p> When there is a positive-width match at the beginning of the input
      * sequence then an empty leading substring is included at the beginning
@@ -1201,8 +1200,6 @@ public final class Pattern
      *          around matches of this pattern
      */
     public String[] split(CharSequence input, int limit) {
-        if (input.length() == 0)
-            return new String[0];
         int index = 0;
         boolean matchLimited = limit > 0;
         ArrayList<String> matchList = new ArrayList<>();
@@ -5774,8 +5771,6 @@ NEXT:       while (i <= last) {
      * the resulting stream has just one element, namely the input sequence in
      * string form.
      *
-     * <p> A zero-length input sequence always results an empty stream.
-     *
      * <p> When there is a positive-width match at the beginning of the input
      * sequence then an empty leading substring is included at the beginning
      * of the stream. A zero-width match at the beginning however never produces

test/java/lang/String/Split.java

@@ -81,8 +81,10 @@ public class Split {
         // split() now returns 0-length for empty source "" see #6559590
         source = "";
         String[] result = source.split("e", 0);
-        if (result.length != 0)
+        if (result.length != 1)
             throw new RuntimeException("String.split failure 8");
+        if (!result[0].equals(source))
+            throw new RuntimeException("String.split failure 9");
 
         // check fastpath of String.split()
         source = "0123456789abcdefgABCDEFG";

test/java/util/regex/RegExTest.java

@@ -1781,7 +1781,9 @@ public class RegExTest {
         // split() now returns 0-length for empty source "" see #6559590
         source = "";
         result = source.split("e", 0);
-        if (result.length != 0)
+        if (result.length != 1)
+            failCount++;
+        if (!result[0].equals(source))
             failCount++;
 
         // Check both split() and splitAsStraem(), especially for zero-lenth
@@ -1817,8 +1819,8 @@ public class RegExTest {
             { "Abc", "Efg", "Hij" },
             { "Abc", "Efg" },
             { "Abc" },
-            {},
-            {},
+            { "" },
+            { "" },
 
             { "awgqwefg1fefw", "vssv1vvv1" },
             { "afbfq", "bgwgb", "wngnwggw", "", "hjrnhneerh" },
@@ -1826,7 +1828,7 @@ public class RegExTest {
             { "a\u4ebafg", "fefw\u4eba4\u9f9cvssv\u9f9c", "v\u672c\u672cvv" },
             { "1", "23", "456", "7890" },
             { "1", "23\u9f9c\u672c\u672c", "456", "\u9f9c\u672c7890" },
-            {},
+            { "" },
             { "This", "is", "testing", "", "with", "different", "separators" },
             { "b", "", ":and:f" },
             { "b", "", "", "", "", ":and:f" },
@@ -1834,12 +1836,16 @@ public class RegExTest {
         };
         for (int i = 0; i < input.length; i++) {
             pattern = Pattern.compile(input[i][0]);
-            if (!Arrays.equals(pattern.split(input[i][1]), expected[i]))
+            if (!Arrays.equals(pattern.split(input[i][1]), expected[i])) {
                 failCount++;
-            if (!Arrays.equals(pattern.splitAsStream(input[i][1]).toArray(),
-                               expected[i]))
+            }
+            if (input[i][1].length() > 0 &&  // splitAsStream() return empty resulting
+                                             // array for zero-length input for now
+                !Arrays.equals(pattern.splitAsStream(input[i][1]).toArray(),
+                               expected[i])) {
                 failCount++;
             }
+        }
         report("Split");
     }