[Java Tutorial #8] - How to create SP to Vests Converter Calculator Aplication using Netbeans

Repository

https://github.com/dmlloyd/openjdk

What Will I Learn?

• You will learn How to create GUI form for this aplication
• You will learn API to convert SP to VEST
• You will learn how to get data from user input and multiply it with the price from API URL
• You will learn how to display last data to the form

Requirements

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

Difficulty

• Basic

Tutorial Contents

In this tutorial, I will try to explain how to make a calculator application to convert steem power to vest. The user inputs the amount of steam power and the system will issue amounts in the vests. Here is what the app looks like:

Let's start the tutorial :

• Open Netbeans IDE software and create new project. Choose Java Aplication and click next. Then Rename the project and click finish.

• Add new jFrameForm in your Source Package
  

• Click on panel component and drag it to the form
  

• Add Label, TextField and Button on Panel, just follow the components on picture bellow :
  

• We already have a form, Now open source and start to edit the code.

• Create The method to get Data from URL. This method in java.net.* method. So before your start use this method import the package first

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;

• Then create a method to read url from web

public String getApi(String url) throws Exception{
        URL oracle=new URL(url);
        HttpURLConnection httpcon = (HttpURLConnection) oracle.openConnection();
        httpcon.addRequestProperty("User-Agent", "Mozilla/5.0");
        BufferedReader in = new BufferedReader(new InputStreamReader(httpcon.getInputStream()));
        String inputLine;
         while ((inputLine = in.readLine()) != null){
             return inputLine;
         }  
        in.close();
        return null;   
    }

Code	Explanation
getApi()	Method Name
String url	The Parameter
throws Exception	Some method to catch error
URL oracle=new URL(url);	Decrlarating new URL
HttpURLConnection httpcon = (HttpURLConnection) oracle.openConnection();	class initiation to get URL connection.
httpcon.addRequestProperty("User-Agent", "Mozilla/5.0");	Add browser property, Here I add Mozilla 5.-0
BufferedReader in = new BufferedReader(new InputStreamReader(httpcon.getInputStream()));	method Read input from http connection.
return inputLine;	return the output
in.close();	close input stream reader

---

• Now create a method to count vests in Steem power

public void calc() throws Exception{
       String Data = getApi("https://uploadbeta.com/api/steemit/converter/?cached");
       JSONObject ObjData=new JSONObject(Data);
       vest.setText(""+Double.parseDouble(sp.getText())*ObjData.getDouble("sp_to_vests"));
    }

Code	Explanation
calc()	Method Name
getApi	we call the previous method to get Data from URL. and the parameter is URL from https://helloacm.com/tools/steemit/
JSONObject ObjData=new JSONObject(Data);	convert the result from string to JSON Object. Here we need use java-json library. Dowload it here : http://www.java2s.com/Code/Jar/j/Downloadjavajsonjar.htm . Extract and add to project Libraries. Then import it to your file, then import org.json package
vests.setText	setText method for vest convert result
Double.parseDouble(sp.getText())	get double value from user input
ObjData.getDouble("sp_to_vests")	get sp price in vests from object data API
""+	The Variable that will be set as text in componen, because the variabel type is double we need combine with a string. So I use ""+.

---

• Call the calc() method in convert button. Open the aplication design form and double click on button. then add this code.

    private void convertActionPerformed(java.awt.event.ActionEvent evt) {                                        
        try {
            calc();
        } catch (Exception ex) {
            Logger.getLogger(calculator.class.getName()).log(Level.SEVERE, null, ex);
        }
    }                                       

• save all code, and try to run the app
  

• Finish, the aplication is running rightly. You can get the full code on my gist. The link is bellow

Curriculum

• [Java Tutorial] - How to create some java aplication to display Live SBD price from bittrex API using Netbeans
• [Java Tutorial #2] - How to create GUI aplication for displaying Live SBD price using Netbeans
• [Java Tutorial #3] - How to create GUI java aplication for displaying Steemit account data using Netbeans
• [Java Tutorial #4] - How to create Calculator java aplication to convert STEEM to IDR using Netbeans
• [Java Tutorial #5] - How to create GUI java aplication for checking The Estimated Reward in Last Week using Netbeans
• [Java Tutorial #6] - How to create GUI java aplication for checking STEEM POWER DETAIL using Netbeans
• [Java Tutorial #7] - How to create Converter Calculator Aplication for STEEM and SBD using Netbeans

Proof of Work Done

https://gist.github.com/team2dev/a5f030cd6f5a78b460ca248786da0937