import javax.swing.JOptionPane;

public class Repeat
{
    
public void whileLoop()
{
    int num, k = 0;
    String input, numStr, result = "";
    input = JOptionPane.showInputDialog("Repeat what?");
    numStr = JOptionPane.showInputDialog("How many times");
    num = Integer.parseInt(numStr);
    while (k < num)
    {   result = result + input + "\n";
        k++;
    }
    JOptionPane.showMessageDialog(null, result);    
}

public void doubleTheMoney()
{   String amountStr = JOptionPane.showInputDialog("Initial amount? ");
    double amount = Double.parseDouble(amountStr);
    double initialAmount = amount;
    String rateStr = JOptionPane.showInputDialog("Interest rate? ");
    double rate = Double.parseDouble(rateStr);
    int year = 0; double interest;
    while (amount < 2 * initialAmount)
    {   interest = amount * rate;
        amount = amount + interest;
        year++;
        System.out.println("year: " + year + "amount: " + amount);
    }
    JOptionPane.showMessageDialog(null, "amount is $" + amount + " after " + year + " years.");
}

public void forLoopExample()
{   int k;
    for (k = 0; k < 20; k++)
        System.out.println("k: " + k + "Happy Thursday"); 
}

public void nestedLoops()
{   int row, col;
    String result = "";
    for (row = 0; row < 7; row++)
    {
        for (col = 0; col <= row; col++)
        {
            result = result + "*";
        }
        result = result + "\n";
    }
    JOptionPane.showMessageDialog(null, result);
}

public static void main(String[] args)
{   Repeat r = new Repeat();
    //r.whileLoop();  
    //r.doubleTheMoney();
    //r.forLoopExample();
    r.nestedLoops();
}
}