import javax.swing.JOptionPane;

public class Ch6
{   int i, sum;
    
    // prints 4 rows of output:
    public void whileLoop1()    
    {   i = 0; sum = 0;
        while (sum < 10)
        {   i++; sum = sum + i;
            System.out.println("i: " + i + " sum: " + sum);
        }
    }
    
    // has an infinite loop:
    public void whileLoop2()    
    {   i = 0; sum = 0;
        while (sum < 10)
        {   i++; sum = sum - i;
            System.out.println("i: " + i + " sum: " + sum);
        } 
    }
    
    // loop never runs:
    public void whileLoop3()    
    {   i = 0; sum = 0;
        while (sum < 0)
        {   i++; sum = sum - i;
            System.out.println("i: " + i + " sum: " + sum);
        }
    }
    
    // loop never runs:
    public void whileLoop4()    
    { i = 0; sum = 0;
        while (sum >= 10)
        {   i++; sum = sum + i;
            System.out.println("i: " + i + " sum: " + sum);
        }
        
    }
    
    // infinite loop.  the semi-colon after the while statement
    // ends the loop.  since 'sum' is always less than 10,
    // the loop runs forever.
    public void whileLoop5()    
    { i = 0; sum = 0;
        while (sum < 10) ;
        {   i++; sum = sum + i;
            System.out.println("i: " + i + " sum: " + sum);
        }
    }
    
    // how long will it take to reach a financial goal?
    public void addInterest()
    {   double interestRate = 0.04;
        double goal = 1000;
        double balance = 500;
        int years = 0;
        while (balance < goal)
        {   double interest = balance * interestRate;
            balance = balance + interest;
            years++;
            String msg = "After " + years + " years, the balance is ";
            msg += balance;
            System.out.println(msg);
        }       
        String msg = "After " + years + " years, the balance is ";
        msg += balance;
        System.out.println(msg);
    }
    
    public void forLoops()
    {   int i;
        // prints 0 1 2 3 4 5
        for (i = 0; i <= 5; i++)
            System.out.print(i + " ");
          
        // prints 5 4 3 2 1 0
        for (i = 5; i >= 0; i--)
             System.out.print(i + " ");
           
        // prints 0 2 4 6 8
        for (i = 0; i < 9; i = i + 2)
             System.out.print(i + " ");
          
        // prints 0 2 4 6 8 10 12 --- [infinite loop]
        for (i = 0; i != 9; i = i + 2)
             System.out.print(i + " ");

        // prints M e t u c h e n
        String str = "Metuchen";
        for (i = 0; i < str.length(); i++)
             System.out.print(str.charAt(i) + " ");
    }
    
    public void forLoop2()
    {   double balance = 500, interestRate;
        String msg = "Run for how many years?";
        String yearsStr = JOptionPane.showInputDialog(msg);
        int years = Integer.parseInt(yearsStr);
        String msg2 = "Interest rate?";
        String rateStr = JOptionPane.showInputDialog(msg2);
        interestRate = Double.parseDouble(rateStr);
        for (int year = 0; year < years; year++)
        {   double interest = balance * interestRate;
            balance = balance + interest;
        }
        System.out.println("balance: " + balance);
    }
    
    // prints 3 rows, with 4 stars in each row
    public void nestedLoops1()
    {   int i, j;
        for (i = 1; i <= 3; i++)
        {   
            for (j = 1; j <= 4; j++)
            {   
                System.out.print("*");
            }
            System.out.println();
        }              
    }
    
    // prints 4 rows, with 3 stars in each row
    public void nestedLoops2()
    {   int i, j;
        for (i = 1; i <= 4; i++)
        {   
            for (j = 1; j <= 3; j++)
            {   
                System.out.print("*");
            }
            System.out.println();
        }              
    }
    
    // prints 1 star on row 1, 2 stars on row 2, etc.
    public void nestedLoops3()
    {   int i, j;
        for (i = 1; i <= 4; i++)
        {   
            for (j = 1; j <= i; j++)
            {   
                System.out.print("*");
            }
            System.out.println();
        }              
    }
    
    // prints 3 rows, with 2 stars in each row
    public void nestedLoops4()
    {   int i, j;
        for (i = 1; i <= 3; i++)
        {   
            for (j = 1; j <= 5; j++)
            {   
                if (j % 2 == 0)
                    System.out.print("*");
            }
            System.out.println();
        }              
    }
    
    // prints 4 rows. Each row alternates * and -
    public void nestedLoops5()
    {   int i, j;
        for (i = 1; i <= 4; i++)
        {   
            for (j = 1; j <= 5; j++)
            {   
                if ((i+j) % 2 == 0)
                    System.out.print("*"); 
                else
                    System.out.print("-");
            }
            System.out.println();
        }              
    }
    
    public static void main(String[] args)
    {   Ch6 c = new Ch6();
        //c.whileLoop1();
        //c.whileLoop2();
        //c.whileLoop3();
        //c.whileLoop4();
        //c.whileLoop5();
        //c.addInterest();
        //c.forLoops();
        //c.forLoop2();
        //c.nestedLoops1();
        //c.nestedLoops2();
        //c.nestedLoops3();
        //c.nestedLoops4();
        c.nestedLoops5();
        
    }
}