Here you can find the source as part of lakeFS and with the help of github it will also render the documentation - https://github.com/treeverse/lakeFS/tree/master/clients/java

package lakefs;

import io.lakefs.clients.api.ApiException;
import io.lakefs.clients.api.model.CommitList;
import io.lakefs.clients.api.model.DiffList;
import io.lakefs.clients.api.model.Error;
import io.lakefs.clients.api.model.Merge;
import io.lakefs.clients.api.model.MergeResult;
import io.lakefs.clients.api.model.RefsDump;
import io.lakefs.clients.api.RefsApi;
import io.lakefs.clients.api.ApiClient;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Client {
    public static void main(String[] args) throws Exception {
        ApiClient client = new ApiClient();
        //client.setDebugging(true);
        client.setBasePath("<http://localhost:8000/api/v1>");
        client.setUsername("<user credentials key>");
        client.setPassword("<user credentials secret");
        //client.setConnectTimeout(0);
        //client.setReadTimeout(0);
        //client.setWriteTimeout(0);
        // ...
    }
}

Sample main with how to setup API client - depends on which API you need to call, you will require to instantiate API class that use this client.

I am trying to hit this API /repositories/{repository}/refs/{ref}/objects

but I am getting error {"message":"parameter \"path\" in query has an error: value is required but missing: value is required but missing"}

what should I pass with this path parameter

could you please give me example

Can you paste the API call you question about and the expected result you like to get from calling it?