Make JWT constants final values

lib/src/main/java/com/auth0/jwt/HeaderParams.java

@@ -10,20 +10,20 @@ private HeaderParams() {}
     /**
      * The algorithm used to sign a JWT.
      */
-    public static String ALGORITHM = "alg";
+    public static final String ALGORITHM = "alg";
 
     /**
      * The content type of the JWT.
      */
-    public static String CONTENT_TYPE = "cty";
+    public static final String CONTENT_TYPE = "cty";
 
     /**
      * The media type of the JWT.
      */
-    public static String TYPE = "typ";
+    public static final String TYPE = "typ";
 
     /**
      * The key ID of a JWT used to specify the key for signature validation.
      */
-    public static String KEY_ID = "kid";
+    public static final String KEY_ID = "kid";
 }

lib/src/main/java/com/auth0/jwt/RegisteredClaims.java

@@ -13,43 +13,43 @@ private RegisteredClaims() {
      * The "iss" (issuer) claim identifies the principal that issued the JWT.
      * Refer RFC 7529 <a href="https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.1">Section 4.1.1</a>
      */
-    public static String ISSUER = "iss";
+    public static final String ISSUER = "iss";
 
     /**
      * The "sub" (subject) claim identifies the principal that is the subject of the JWT.
      * Refer RFC 7529 <a href="https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.2">Section 4.1.2</a>
      */
-    public static String SUBJECT = "sub";
+    public static final String SUBJECT = "sub";
 
     /**
      * The "aud" (audience) claim identifies the recipients that the JWT is intended for.
      * Refer RFC 7529 <a href="https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.3">Section 4.1.3</a>
      */
-    public static String AUDIENCE = "aud";
+    public static final String AUDIENCE = "aud";
 
     /**
      * The "exp" (expiration time) claim identifies the expiration time on or after which the JWT MUST NOT be
      * accepted for processing.
      * Refer RFC 7529 <a href="https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.4">Section 4.1.4</a>
      */
-    public static String EXPIRES_AT = "exp";
+    public static final String EXPIRES_AT = "exp";
 
     /**
      * The "nbf" (not before) claim identifies the time before which the JWT MUST NOT be accepted for processing.
      * Refer RFC 7529 <a href="https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.5">Section 4.1.5</a>
      */
-    public static String NOT_BEFORE = "nbf";
+    public static final String NOT_BEFORE = "nbf";
 
     /**
      * The "iat" (issued at) claim identifies the time at which the JWT was issued.
      * Refer RFC 7529 <a href="https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.6">Section 4.1.6</a>
      */
-    public static String ISSUED_AT = "iat";
+    public static final String ISSUED_AT = "iat";
 
     /**
      * The "jti" (JWT ID) claim provides a unique identifier for the JWT.
      * Refer RFC 7529 <a href="https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.7">Section 4.1.7</a>
      */
-    public static String JWT_ID = "jti";
+    public static final String JWT_ID = "jti";
 
 }