Can i add proxy to the dopbox api?

Yes, if you're using the official API v2 Java SDK, you can set a proxy by constructing a StandardHttpRequestor with a StandardHttpRequestor.Config. You can build a StandardHttpRequestor.Config with a proxy set by using StandardHttpRequestor.Config.builder to get a StandardHttpRequestor.Config.Builder and using the withProxy method.

That would look something like:

StandardHttpRequestor.Config.Builder requestorConfigBuilder = StandardHttpRequestor.Config.builder();
requestorConfigBuilder.withProxy(yourProxy);
StandardHttpRequestor.Config requestorConfig = requestorConfigBuilder.build();
StandardHttpRequestor requestor = new StandardHttpRequestor(requestorConfig);

DbxRequestConfig requestConfig = DbxRequestConfig.newBuilder("testApp/")
        .withHttpRequestor(requestor)
        .build();

DbxClientV2 client = new DbxClientV2(requestConfig, ACCESS_TOKEN);