Avoid temporary String creation in StringUtils.starts/endsWithIgnoreCase

Issue: SPR-16095

spring-core/src/main/java/org/springframework/util/StringUtils.java

@@ -164,7 +164,7 @@ public abstract class StringUtils {
 			}
 		}
 		return false;
-}
+	}
 
 	/**
 	 * Check whether the given {@code CharSequence} contains any whitespace characters.
@@ -314,7 +314,6 @@ public abstract class StringUtils {
 		return sb.toString();
 	}
 
-
 	/**
 	 * Test if the given {@code String} starts with the specified prefix,
 	 * ignoring upper/lower case.
@@ -323,19 +322,8 @@ public abstract class StringUtils {
 	 * @see java.lang.String#startsWith
 	 */
 	public static boolean startsWithIgnoreCase(@Nullable String str, @Nullable String prefix) {
-		if (str == null || prefix == null) {
-			return false;
-		}
-		if (str.startsWith(prefix)) {
-			return true;
-		}
-		if (str.length() < prefix.length()) {
-			return false;
-		}
-
-		String lcStr = str.substring(0, prefix.length()).toLowerCase();
-		String lcPrefix = prefix.toLowerCase();
-		return lcStr.equals(lcPrefix);
+		return (str != null && prefix != null && str.length() >= prefix.length() &&
+				str.regionMatches(true, 0, prefix, 0, prefix.length()));
 	}
 
 	/**
@@ -346,19 +334,8 @@ public abstract class StringUtils {
 	 * @see java.lang.String#endsWith
 	 */
 	public static boolean endsWithIgnoreCase(@Nullable String str, @Nullable String suffix) {
-		if (str == null || suffix == null) {
-			return false;
-		}
-		if (str.endsWith(suffix)) {
-			return true;
-		}
-		if (str.length() < suffix.length()) {
-			return false;
-		}
-
-		String lcStr = str.substring(str.length() - suffix.length()).toLowerCase();
-		String lcSuffix = suffix.toLowerCase();
-		return lcStr.equals(lcSuffix);
+		return (str != null && suffix != null && str.length() >= suffix.length() &&
+				str.regionMatches(true, str.length() - suffix.length(), suffix, 0, suffix.length()));
 	}
 
 	/**
@@ -369,9 +346,11 @@ public abstract class StringUtils {
 	 * @param substring the substring to match at the given index
 	 */
 	public static boolean substringMatch(CharSequence str, int index, CharSequence substring) {
-		for (int j = 0; j < substring.length(); j++) {
-			int i = index + j;
-			if (i >= str.length() || str.charAt(i) != substring.charAt(j)) {
+		if (index + substring.length() > str.length()) {
+			return false;
+		}
+		for (int i = 0; i < substring.length(); i++) {
+			if (str.charAt(index + i) != substring.charAt(i)) {
 				return false;
 			}
 		}

spring-core/src/test/java/org/springframework/util/StringUtilsTests.java

@@ -138,6 +138,56 @@ public class StringUtilsTests {
 		assertEquals(" a b  c", StringUtils.trimTrailingCharacter(" a b  c ", ' '));
 	}
 
+	@Test
+	public void testStartsWithIgnoreCase() {
+		String suffix = "fOo";
+		assertTrue(StringUtils.startsWithIgnoreCase("foo", suffix));
+		assertTrue(StringUtils.startsWithIgnoreCase("Foo", suffix));
+		assertTrue(StringUtils.startsWithIgnoreCase("foobar", suffix));
+		assertTrue(StringUtils.startsWithIgnoreCase("foobarbar", suffix));
+		assertTrue(StringUtils.startsWithIgnoreCase("Foobar", suffix));
+		assertTrue(StringUtils.startsWithIgnoreCase("FoobarBar", suffix));
+		assertTrue(StringUtils.startsWithIgnoreCase("foObar", suffix));
+		assertTrue(StringUtils.startsWithIgnoreCase("FOObar", suffix));
+		assertTrue(StringUtils.startsWithIgnoreCase("fOobar", suffix));
+		assertFalse(StringUtils.startsWithIgnoreCase(null, suffix));
+		assertFalse(StringUtils.startsWithIgnoreCase("fOobar", null));
+		assertFalse(StringUtils.startsWithIgnoreCase("b", suffix));
+	}
+
+	@Test
+	public void testEndsWithIgnoreCase() {
+		String suffix = "fOo";
+		assertTrue(StringUtils.endsWithIgnoreCase("foo", suffix));
+		assertTrue(StringUtils.endsWithIgnoreCase("Foo", suffix));
+		assertTrue(StringUtils.endsWithIgnoreCase("barfoo", suffix));
+		assertTrue(StringUtils.endsWithIgnoreCase("barbarfoo", suffix));
+		assertTrue(StringUtils.endsWithIgnoreCase("barFoo", suffix));
+		assertTrue(StringUtils.endsWithIgnoreCase("barBarFoo", suffix));
+		assertTrue(StringUtils.endsWithIgnoreCase("barfoO", suffix));
+		assertTrue(StringUtils.endsWithIgnoreCase("barFOO", suffix));
+		assertTrue(StringUtils.endsWithIgnoreCase("barfOo", suffix));
+		assertFalse(StringUtils.endsWithIgnoreCase(null, suffix));
+		assertFalse(StringUtils.endsWithIgnoreCase("barfOo", null));
+		assertFalse(StringUtils.endsWithIgnoreCase("b", suffix));
+	}
+
+	@Test
+	public void testSubstringMatch() {
+		assertTrue(StringUtils.substringMatch("foo", 0, "foo"));
+		assertTrue(StringUtils.substringMatch("foo", 1, "oo"));
+		assertTrue(StringUtils.substringMatch("foo", 2, "o"));
+		assertFalse(StringUtils.substringMatch("foo", 0, "fOo"));
+		assertFalse(StringUtils.substringMatch("foo", 1, "fOo"));
+		assertFalse(StringUtils.substringMatch("foo", 2, "fOo"));
+		assertFalse(StringUtils.substringMatch("foo", 3, "fOo"));
+		assertFalse(StringUtils.substringMatch("foo", 1, "Oo"));
+		assertFalse(StringUtils.substringMatch("foo", 2, "Oo"));
+		assertFalse(StringUtils.substringMatch("foo", 3, "Oo"));
+		assertFalse(StringUtils.substringMatch("foo", 2, "O"));
+		assertFalse(StringUtils.substringMatch("foo", 3, "O"));
+	}
+
 	@Test
 	public void testCountOccurrencesOf() {
 		assertTrue("nullx2 = 0",
@@ -579,23 +629,6 @@ public class StringUtilsTests {
 		assertTrue("Output equals input", Arrays.equals(sa, components));
 	}
 
-	@Test
-	public void testEndsWithIgnoreCase() {
-		String suffix = "fOo";
-		assertTrue(StringUtils.endsWithIgnoreCase("foo", suffix));
-		assertTrue(StringUtils.endsWithIgnoreCase("Foo", suffix));
-		assertTrue(StringUtils.endsWithIgnoreCase("barfoo", suffix));
-		assertTrue(StringUtils.endsWithIgnoreCase("barbarfoo", suffix));
-		assertTrue(StringUtils.endsWithIgnoreCase("barFoo", suffix));
-		assertTrue(StringUtils.endsWithIgnoreCase("barBarFoo", suffix));
-		assertTrue(StringUtils.endsWithIgnoreCase("barfoO", suffix));
-		assertTrue(StringUtils.endsWithIgnoreCase("barFOO", suffix));
-		assertTrue(StringUtils.endsWithIgnoreCase("barfOo", suffix));
-		assertFalse(StringUtils.endsWithIgnoreCase(null, suffix));
-		assertFalse(StringUtils.endsWithIgnoreCase("barfOo", null));
-		assertFalse(StringUtils.endsWithIgnoreCase("b", suffix));
-	}
-
 
 	@Test
 	public void testParseLocaleStringSunnyDay() {