add feature convert Unicode to Hexadecimal code.

README.md

@@ -155,6 +155,28 @@ System.out.println(resultHexadecimal);
 // "An 😀awesome 😃string with a few 😉emojis!"
 ```
 
+#### To hexadecimal
+
+To replace all the emoji's unicodes found in a string by their hexadecimal codes representation, use `EmojiParser#parseToStringHexadecimalWithEscapeSequences(String)` or `EmojiParser#parseToStringHexadecimalWithEscapeSequences(String)`.
+
+For example:
+
+```java
+String str1 = "Hello World! 😀";
+
+String resultHexadecimal1 = EmojiParser.parseToHtmlDecimal(str1);
+System.out.println(resultHexadecimal1);
+// Prints:
+// "Hello World! \\ud83d\\ude00"
+
+String str2 = "An 😀awesome 😃string with a few 😉emojis!";
+
+String resultHexadecimal2 = EmojiParser.parseToStringHexadecimalWithEscapeSequences(str2);
+System.out.println(resultHexadecimal2);
+// Prints:
+// "An \\ud83d\\ude00awesome \\ud83d\\ude03string with a few \\ud83d\\ude09emojis!"
+```
+
 By default, any Fitzpatrick modifier will be removed. If you want to ignore the Fitzpatrick modifiers, use `EmojiParser#parseToAliases(String, FitzpatrickAction)`. Examples:
 
 ```java

src/main/java/com/vdurmont/emoji/Emoji.java

@@ -19,6 +19,7 @@ public class Emoji {
   private final String unicode;
   private final String htmlDec;
   private final String htmlHex;
+  private final String stringHex;
 
   /**
    * Constructor for the Emoji.
@@ -47,21 +48,32 @@ protected Emoji(
       int stringLength = getUnicode().length();
       String[] pointCodes = new String[stringLength];
       String[] pointCodesHex = new String[stringLength];
+      String[] pointCodesStringHex = new String[stringLength];
 
       for (int offset = 0; offset < stringLength; ) {
         final int codePoint = getUnicode().codePointAt(offset);
 
         pointCodes[count] = String.format("&#%d;", codePoint);
-        pointCodesHex[count++] = String.format("&#x%x;", codePoint);
+        pointCodesHex[count] = String.format("&#x%x;", codePoint);
+        pointCodesStringHex[count++] = convertEscapeSequence(codePoint);
 
         offset += Character.charCount(codePoint);
       }
       this.htmlDec = stringJoin(pointCodes, count);
       this.htmlHex = stringJoin(pointCodesHex, count);
+      this.stringHex = stringJoin(pointCodesStringHex, count);
     } catch (UnsupportedEncodingException e) {
       throw new RuntimeException(e);
     }
   }
+
+  public String convertEscapeSequence(int codePoint) {
+      String scapes = "";
+      for(char c : new StringBuilder().appendCodePoint(codePoint).toString().toCharArray()) {
+          scapes += "\\\\u"+String.valueOf(Integer.toHexString(c));
+      }
+      return scapes;
+  }
 
   /**
    * Method to replace String.join, since it was only introduced in java8
@@ -211,4 +223,13 @@ public String toString() {
       ", htmlHex='" + htmlHex + '\'' +
       '}';
   }
+
+  /**
+   * Returns the string codepoint representation of the emoji
+   *
+   * @return the String codepoint hexadecimal representation 
+   */
+  public String getStringHexadecimalWithEscapeSequences() {
+      return this.stringHex;
+  }
 }

src/main/java/com/vdurmont/emoji/EmojiParser.java

@@ -4,6 +4,10 @@
 import java.util.Collection;
 import java.util.List;
 
+import com.vdurmont.emoji.EmojiParser.EmojiTransformer;
+import com.vdurmont.emoji.EmojiParser.FitzpatrickAction;
+import com.vdurmont.emoji.EmojiParser.UnicodeCandidate;
+
 /**
  * Provides methods to parse strings with emojis.
  *
@@ -573,4 +577,38 @@ public enum FitzpatrickAction {
   public interface EmojiTransformer {
     String transform(UnicodeCandidate unicodeCandidate);
   }
+
+  /**
+   * See {@link #parseToStringHexadecimalWithEscapeSequences(String, FitzpatrickAction)} with the
+   * action "PARSE"
+   *
+   * @param input the string to parse
+   *
+   * @return the string with the emojis replaced by their text hex
+   * representation.
+   */
+  public static String parseToStringHexadecimalWithEscapeSequences(String input) {
+      return parseToStringHexadecimalWithEscapeSequences(input, FitzpatrickAction.PARSE);
+  }
+
+  public static String parseToStringHexadecimalWithEscapeSequences(
+          String input,
+          final FitzpatrickAction fitzpatrickAction
+        ) {
+          EmojiTransformer emojiTransformer = new EmojiTransformer() {
+            public String transform(UnicodeCandidate unicodeCandidate) {
+              switch (fitzpatrickAction) {
+                default:
+                case PARSE:
+                case REMOVE:
+                  return unicodeCandidate.getEmoji().getStringHexadecimalWithEscapeSequences();
+                case IGNORE:
+                  return unicodeCandidate.getEmoji().getStringHexadecimalWithEscapeSequences() +
+                    unicodeCandidate.getFitzpatrickUnicode();
+              }
+            }
+          };
+
+          return parseFromUnicode(input, emojiTransformer);
+    }
 }

src/test/java/com/vdurmont/emoji/EmojiParserTest.java

@@ -550,4 +550,16 @@ public void parseToAliases_with_first_medal() {
     // THEN
     assertEquals(":first_place_medal:", result);
   }
+
+  @Test
+  public void parseToAliases_with_first_medala() {
+    // GIVEN
+    String str = "Hello World! 😀";
+
+    // WHEN
+    String result = EmojiParser.parseToStringHexadecimalWithEscapeSequences(str);
+
+    // THEN
+    assertEquals("Hello World! \\\\ud83d\\\\ude00", result);
+  }
 }