Examples Using the for Statement

Total even integers from 2 through 20:

// Fig. 5.5: Sum.java
// Summing integers with the for statement.

public class Sum 
{
   public static void main( String[] args )
   {
      int total = 0; // initialize total

      // total even integers from 2 through 20
      for ( int number = 2; number <= 20; number += 2 )
         total += number;

      System.out.printf( "Sum is %d\n", total ); // display results
   } // end main
} // end class Sum

Compound interest application

A person invests $1000 in a savings account yielding 5% interest. Assuming that all the interest is left on deposit, calculate and print the amount of money in the account at the end of each year for 10 years. Use the following formula to determine the amounts

a = p (1 + r)n

where

p is the original amount invested (i.e., the principal)
r is the annual interest rate (e.g., use 0.05 for 5%)
n is the number of years
a is the amount on deposit at the end of the nth year

// Fig. 5.6: Interest.java
// Compound-interest calculations with for.

public class Interest 
{
   public static void main( String args[] )
   {
      double amount; // amount on deposit at end of each year
      double principal = 1000.0; // initial amount before interest
      double rate = 0.05; // interest rate

      // display headers
      System.out.printf( "%s%20s\n", "Year", "Amount on deposit" );

      // calculate amount on deposit for each of ten years
      for ( int year = 1; year <= 10; year++ ) 
      {
         // calculate new amount for specified year
         amount = principal * Math.pow( 1.0 + rate, year );

         // display the year and the amount
         System.out.printf( "%4d%,20.2f\n", year, amount );
      } // end for
   } // end main
} // end class Interest

To indicate that values should be output left justified, precede the field width with the minus sign (–) formatting flag (e.g., %-20s).
In the format specifier %,20.2f, the comma (,) formatting flag indicates that the floating-point value should be output with a grouping separator.  For example, 1,234.45

• Classes provide methods that perform common tasks on objects.
• Most methods must be called on a specific object.
• Many classes also provide methods that perform common tasks and do not require objects. These are called static methods.
• Java does not include an exponentiation operator—Math class static method pow can be used for raising a value to a power.
• You can call a static method by specifying the class name followed by a dot (.) and the method name, as in
  • ClassName.methodName( arguments )
• Math.pow(x, y) calculates the value of x raised to the yth power. The method receives two double arguments and returns a double value.