addition of filledString() method

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

@@ -1852,6 +1852,22 @@ public static boolean equalsIgnoreCase(final CharSequence cs1, final CharSequenc
         return Strings.CI.equals(cs1, cs2);
     }
 
+    /**
+     * Constructs a string of specified length filled with the specified char.
+     * @param length the length of the final string.
+     * @param fillChar the character to file it will.
+     * @return A string of specified length filled with the specified char.
+     * @since 1.10.0
+     */
+    public static String filledString(final int length, final char fillChar) {
+        if (length < 0) {
+            throw new IllegalArgumentException("Length must not be negative");
+        }
+        final char[] padding = new char[length];
+        Arrays.fill(padding, fillChar);
+        return new String(padding);
+    }
+
     /**
      * Returns the first value in the array which is not empty (""),
      * {@code null} or whitespace only.

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

@@ -809,6 +809,13 @@ public void testEscapeSurrogatePairsLang858() {
         assertEquals("\\uDBFF\\uDFFD", StringEscapeUtils.escapeEcmaScript("\uDBFF\uDFFD")); //fail LANG-858
     }
 
+    @Test
+    public void testFilledString() {
+        assertEquals("-----", StringUtils.filledString(5, '-'));
+        assertEquals("", StringUtils.filledString(0, '-'));
+        assertThrows(IllegalArgumentException.class, () -> StringUtils.filledString(-1, '-'));
+    }
+
     @Test
     public void testGeorgianSample() {
         final char[] arrayI = {