[Java Tutorial] - How to create some java aplication to display Live SBD price from bittrex API using Netbeans

Repository

https://github.com/dmlloyd/openjdk

What Will I Learn?

• You will learn How to get data from URL API
• You will learn how to Display data in Java
• You will learn how to split data and dislay ony the important data
• You will learn about JSONObject

Requirements

• Basic knowledges about java programing
• Basic Knowledges about API
• Need to Install Netbeans for easy pratice

Difficulty

• Basic

Tutorial Contents

In this occasion, I will try to create a tutorial how to get data from bittrec API and display it in my JAVA aplication. For Sample, I wanna to display LIVE SBD price. You can try for other criptocurrency.

In Java Programming, To get data from some URL we can use net.URL package. By using some functions, We can grab all data from API url and display it in our Aplication. Lets start the tutorial :

• Open Netbeans IDE software and create new project. Choose Java Aplication and click next
  

• Rename the project and click Finish
  

• Open the java file on editor and start to code.
  

• Import net-URL package

import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.Charset;

These all package used to grab data from some URL in web. These package contains some class and some java method to open URL connection and to grab some data from The URL.

• import BufferedReader and IOException package. These package used to read input url and handle the error

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

• Create getData method. This method is to grab data from api URL. The Explanations under the code :

public static String getData(String apiURL) {
        System.out.println("api URL:" + apiURL);
        StringBuilder sb = new StringBuilder();
        URLConnection urlConn = null;
        InputStreamReader in = null;
        try {
            URL url = new URL(apiURL);
            urlConn = url.openConnection();
            if (urlConn != null)
                urlConn.setReadTimeout(60 * 1000);
            if (urlConn != null && urlConn.getInputStream() != null) {
                in = new InputStreamReader(urlConn.getInputStream(),
                        Charset.defaultCharset());
                BufferedReader bufferedReader = new BufferedReader(in);
                if (bufferedReader != null) {
                    int cp;
                    while ((cp = bufferedReader.read()) != -1) {
                        sb.append((char) cp);
                    }
                    bufferedReader.close();
                }
            }
        in.close();
        } catch (IOException e) {
            throw new RuntimeException("Exception while calling URL:"+ apiURL, e);
        } 
 
        return sb.toString();
    }

Code	Explanation
System.out.println("api URL:" + apiURL);	Print the API URL
StringBuilder sb = new StringBuilder(); URLConnection urlConn = null; InputStreamReader in = null;	Instance Class Object.
if (urlConn != null) urlConn.setReadTimeout(60 * 1000);	set time for timeout when the URL is not empty
in = new InputStreamReader(urlConn.getInputStream(), Charset.defaultCharset());	restore the url as input stream
new BufferedReader(in);	Read the URL to grap or get Data
while ((lengthData = bufferedReader.read()) != -1) { sb.append((char) lengthData);}	Displaying data in while looping. this looping start from the index 0 until the end.

• Create the main class to display the data got from URL API. Call the getData class that we have created before. Then add some bittrex API url. you can visit : https://support.bittrex.com/hc/en-us/articles/115003723911-Developer-s-Guide-API for more URL

    public static void main(String[] args) throws JSONException {
       final JSONObject obj = new JSONObject(getData("https://bittrex.com/api/v1.1/public/getmarketsummary?market=btc-sbd"));
    System.out.println(obj);
    }

• Becouse we use JSONObject here we need to add java-json Library. Dowload it here : http://www.java2s.com/Code/Jar/j/Downloadjavajsonjar.htm . Extract and add to project Libraries.
  

• import the JSONObject package

import java.nio.charset.Charset;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONArray;

• save the file and try to run the project
  

• We already get data from URL as JSON. In case we don't need all data. We want just display market-name, timestamp and last-price. SO, now we need to split the JSON data.

    final JSONArray result=obj.getJSONArray("result");
    final int n = result.length();
    for (int i = 0; i < n; ++i) {
      final JSONObject person = result.getJSONObject(i);
       System.out.println("Cryptocurrency :"+person.getString("MarketName"));
       System.out.println("Real Time"+person.getString("TimeStamp"));
       System.out.println("Last Price"+person.getDouble("Last"));
    }

Code	Explanation
final JSONArray result=obj.getJSONArray("result");	Get array value of result.
final int n = result.length();	get result lenght or get data count.
for (int i = 0; i < n; ++i)	looping for here used to display data one by one.
final JSONObject person = result.getJSONObject(i);	istance the class
person.getString("MarketName")	get data from marketName. why we use getString method ? because the value is from string type.

• Save and try to run
  

• Finally we Already split JSON data. What is the problem now. See on the result of lastprice, it display in Double type. If we need to convert it to decimal, what can we do ? we need to add BigDecimal() method like this:

 System.out.println(BigDecimal.valueOf(person.getDouble("Last")));

• Because BigDecimal() is from java.math.BigDecimal package, so you need to import this package :

import java.math.BigDecimal;

• Now, Try to run the project .
  

• You can see now the Last Price is display in Decimal. Now try to display data in Sentence

System.out.println("The Last Price of "+person.getString("MarketName")+" is : "+BigDecimal.valueOf(person.getDouble("Last")));
       System.out.println("Real Time :"+person.getString("TimeStamp"));

• FINISH. We already got data from URL API and display it as our plan. You can try to get dara from other URL API to make you more understand.

Curriculum

This is My first tutorial contributin about JAVA

Proof of Work Done

https://gist.github.com/team2dev/c466b39cd707e9486982c09090874432