Internal: resolve a few compiler warnings

@NotThreadSafe is not a valid standard java annotation. Removed unused method and empty @param javadoc annotation

Original commit: elastic/x-pack-elasticsearch@3583bcfa66

src/main/java/org/elasticsearch/shield/authc/support/SecuredString.java

@@ -13,7 +13,7 @@ import java.util.Arrays;
 /**
  * This is not a string but a CharSequence that can be cleared of its memory.  Important for handling passwords.
  *
- * @NotThreadSafe There is a chance that the chars could be cleared while doing operations on the chars.
+ * Not thread safe There is a chance that the chars could be cleared while doing operations on the chars.
  * <p/>
  * TODO: dot net's SecureString implementation does some obfuscation of the password to prevent gleaming passwords
  * from memory dumps.  (this is hard as dot net uses windows system crypto.  Thats probably the reason java still doesn't have it)
@@ -25,8 +25,6 @@ public class SecuredString implements CharSequence {
     /**
      * Note: the passed in chars are not duplicated, but used directly for performance/optimization.  DO NOT
      * modify or clear the chars after it has been passed into this constructor.
-     *
-     * @param chars
      */
     public SecuredString(char[] chars) {
         this.chars = new char[chars.length];
@@ -127,15 +125,6 @@ public class SecuredString implements CharSequence {
         super.finalize();
     }
 
-    public int indexOf(char toFind) {
-        for (int i = 0; i < chars.length; i++) {
-            if (chars[i] == toFind) {
-                return i;
-            }
-        }
-        return -1;
-    }
-
     /**
      * @param toAppend String to combine with this SecureString
      * @return a new SecureString with toAppend concatenated

src/main/java/org/elasticsearch/shield/authc/support/UsernamePasswordToken.java

@@ -66,7 +66,6 @@ public class UsernamePasswordToken implements AuthenticationToken {
         return Objects.hash(username, password.hashCode());
     }
 
-
     public static UsernamePasswordToken extractToken(TransportMessage<?> message, UsernamePasswordToken defaultToken) {
         String authStr = message.getHeader(BASIC_AUTH_HEADER);
         if (authStr == null) {