Make IsBlank matcher consistent with String.isBlank

hamcrest/src/main/java/org/hamcrest/text/IsBlankString.java

@@ -5,8 +5,6 @@
 import org.hamcrest.Matcher;
 import org.hamcrest.TypeSafeMatcher;
 
-import java.util.regex.Pattern;
-
 import static org.hamcrest.core.AnyOf.anyOf;
 import static org.hamcrest.core.IsNull.nullValue;
 
@@ -18,13 +16,20 @@ public final class IsBlankString extends TypeSafeMatcher<String> {
     @SuppressWarnings("unchecked")
     private static final Matcher<String> NULL_OR_BLANK_INSTANCE = anyOf(nullValue(), BLANK_INSTANCE);
 
-    private static final Pattern REGEX_WHITESPACE = Pattern.compile("\\s*");
-
     private IsBlankString() { }
 
     @Override
     public boolean matchesSafely(String item) {
-        return REGEX_WHITESPACE.matcher(item).matches();
+        final int length = item.length();
+        int offset = 0;
+        while (offset < length) {
+            final int codePoint = item.codePointAt(offset);
+            if (!Character.isWhitespace(codePoint)) {
+                return false;
+            }
+            offset += Character.charCount(codePoint);
+        }
+        return true;
     }
 
     @Override

hamcrest/src/test/java/org/hamcrest/text/IsBlankStringTest.java

@@ -34,6 +34,27 @@ public final class IsBlankStringTest {
         assertMatches(blankString(), " \t");
         assertMatches(blankOrNullString(), " \t");
     }
+
+    @Test public void
+    matchesAllCharactersConsideredWhitespaceByJavaLangCharacter() {
+        // See Javadocs for Character.isWhitespace
+        String[] consideredBlankByJavaLangCharacter = new String[] {
+                "\t",
+                "\n",
+                "\u000B",
+                "\f",
+                "\r",
+                "\u001C",
+                "\u001D",
+                "\u001E",
+                "\u001F"
+        };
+
+        for(String string : consideredBlankByJavaLangCharacter) {
+            assertMatches(blankString(), string);
+            assertMatches(blankOrNullString(), string);
+        }
+    }
 
     @Test public void
     doesNotMatchFilledString() {
@@ -52,4 +73,5 @@ public final class IsBlankStringTest {
         assertMismatchDescription("was \"a\"", blankString(), "a");
         assertMismatchDescription("was \"a\"", blankOrNullString(), "a");
     }
+
 }