Keycloak REST APIs - Get bearer token

GetToken.java

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.LinkedHashMap;
import java.util.Map;

public class GetToken {

    public static void main(String[] args) throws IOException {
        new GetToken().getBearerToken();
    }

    public String getBearerToken() throws IOException{

        String client_id = "login-app";
        String grant_type = "client_credentials";
        String client_secret = "6b574a0b-6624-4d7a-9ac6-485c1fdcc9e0";
        String port = "8081";
        String realm = "api";
        String server = "localhost";
        String content_type = "application/x-www-form-urlencoded";
        String method_type = "POST";
        String encode_type = "UTF-8";

        URL url = new URL("http://"+ server +":"+ port +"/auth/realms/"+ realm +"/protocol/openid-connect/token");

        Map params = new LinkedHashMap();
        params.put("client_id", client_id);
        params.put("grant_type", grant_type);
        params.put("client_secret", client_secret);

        StringBuilder postData = new StringBuilder();
        for(Map.Entry param : params.entrySet()){
            if (postData.length() != 0) postData.append('&');
            postData.append(URLEncoder.encode(param.getKey(), encode_type));
            postData.append('=');
            postData.append(URLEncoder.encode(String.valueOf(param.getValue()), encode_type));
        }

        byte[] postDataBytes = postData.toString().getBytes(encode_type);

        HttpURLConnection conn = (HttpURLConnection)url.openConnection();
        conn.setRequestMethod(method_type);
        conn.setRequestProperty("Content-Type", content_type);
        conn.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
        conn.setDoOutput(true);
        conn.getOutputStream().write(postDataBytes);

        BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream(), encode_type));
        String line;
        StringBuilder result = new StringBuilder();

        while ((line = in.readLine()) != null) {
            result.append(line);
        }
        String response = result.toString();

        String[] array = response.split(",");
        String[] accessToken = array[0].split(":");
        String token = accessToken[1].replace("\"","");

        System.out.println(token);

        return token;
    }
}