/*
 * n_graph4.java
 *
 * Created on 29 Δεκέμβριος 2003, 10:07 πμ
 */



/**
 *
 * @author  gauss
 * @version 
 */
import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class n_graph4 extends  java.applet.Applet implements ActionListener
{   
	TextField textField1 = new TextField(); //input textField
	TextField textField2 = new TextField(); //output textField
	Label label1 = new Label();
	Label label2 = new Label();
        Label label3 = new Label();
	Button button1 = new Button();
	
	public void init()
	{
		
		setLayout(null);  //free layout
		setSize(600,300); //size of this applet
		
		add(textField1); 
                textField1.setForeground(Color.blue);
		textField1.setFont(new Font("Dialog", Font.BOLD, 15));
		textField1.setBounds(100,50,150,30);
	    
		add(textField2);
                textField2.setForeground(Color.green);
		textField2.setFont(new Font("Dialog", Font.BOLD, 15));
		textField2.setBounds(100,120,150,30);
		
		add(label1);
		label1.setText(" πληθος");
		label1.setFont(new Font("Dialog", Font.BOLD, 12));
		label1.setBounds(20,50,70,40);
		
		add(label2);
		label2.setText("αθροισμα");
		label2.setFont(new Font("Dialog", Font.BOLD, 12));
		label2.setBounds(20,120,70,40);
		
                add(label3);
                label3.setBackground(Color.lightGray);
                label3.setForeground(Color.blue);
		label3.setText("υπολογισμος του αθροισματος 1+2+...+n");
		label3.setFont(new Font("Dialog", Font.BOLD, 12));
		label3.setBounds(50,10,250,30);
                
		add(button1);
                button1.setForeground(Color.blue);
		button1.setLabel("υπολογισε");
		button1.setBackground(java.awt.Color.magenta);
		button1.setFont(new Font("Dialog", Font.BOLD, 12));
		button1.setBounds(100,200,120,30);
	    	button1.addActionListener(this);
	
	}
	

	public void actionPerformed(ActionEvent event)
	{
		Object object = event.getSource();
		String str;
		int n,sum;
		if (object == button1){
			 // get text from textfield 
		    	str=textField1.getText();
			// convert string to integer
			n=Integer.parseInt(str);  
			sum=calculate(n);
			// convert integer to string	
	        		str=Integer.toString(sum);	
			//set text to textfield
			textField2.setText(str);  
	    	}
	}
	
	public int calculate(int n){
	    	int i;  // index 
	    	int a;  // i-th term
	    	int s=0;  // sum of the sequence
	    	for(i=1;i<=n;i++){
	        		a=i;    //a(i)=i
	        		s=s+a;  // S(i+1)=S(i)+a(i)
	    	}
	    	return s;
	}	
      
}