Fixed documentation for decr and added @nonnull tags where appropriate.

java/client/src/main/java/glide/api/BaseClient.java

@@ -181,12 +181,12 @@ public CompletableFuture<String> set(
     }
 
     @Override
-    public CompletableFuture<Long> decr(String key) {
+    public CompletableFuture<Long> decr(@NonNull String key) {
         return commandManager.submitNewCommand(Decr, new String[] {key}, this::handleLongResponse);
     }
 
     @Override
-    public CompletableFuture<Long> decrBy(String key, long amount) {
+    public CompletableFuture<Long> decrBy(@NonNull String key, long amount) {
         return commandManager.submitNewCommand(
                 DecrBy, new String[] {key, Long.toString(amount)}, this::handleLongResponse);
     }

java/client/src/main/java/glide/api/commands/StringCommands.java

@@ -50,16 +50,14 @@ public interface StringCommands {
     CompletableFuture<String> set(String key, String value, SetOptions options);
 
     /**
-     * Increment the string representing a floating point number stored at <code>key</code> by <code>
-     * amount</code>. By using a negative increment value, the result is that the value stored at
-     * <code>key</code> is decremented. If <code>key</code> does not exist, it is set to 0 before
-     * performing the operation.
+     * Decrements the number stored at <code>key</code> by one. If <code>key</code> does not exist, it
+     * is set to 0 before performing the operation.
      *
      * @see <a href="https://redis.io/commands/decr/">redis.io</a> for details.
-     * @param key The key to increment its value.
-     * @return The value of <code>key</code> after the increment. An error is raised if <code>key
-     *     </code> contains a value of the wrong type, or the current <code>key</code> content is not
-     *     parsable as a double precision floating point number.
+     * @param key The key to decrement its value.
+     * @return The value of <code>key</code> after the decrement. An error is raised if <code>key
+     *     </code> contains a value of the wrong type or contains a string that cannot be represented
+     *     as integer.
      */
     CompletableFuture<Long> decr(String key);