FURTHER EXAMPLES ILLUSTRATING THE USE OF THE JAVA SWITCH SRAREMENT

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CONTENTS

1. Date validation


1. DATE VALIDATION.

The code given in Table 1 describes a class which can be used to validate dates input using the DDMMYYYY format. For example the date 1-11-200 would be written as --- 1112000. To obtain the "day-month-year" elements from a number N of this format we proceed as follows:

  1. Divide N by 1000000 (using "integer division") to obtain the day.
  2. Divide the remainder of N/1000000 by 10000 to obtain the month.
  3. Calculate the remainder of N/10000 to obtain the year.

Example, given N=1112000 (1-11-200):

day   = 1112000/1000000         = 1
month = (1112000%1000000)/10000 = 
	112000/10000            = 11
year  = 1112000%10000           = 2000

Note that, from the code presented in Table 1, the cases in a switch statement do not have to be ordered in any way but can be grouped together in anyway as dictated by the application.

The rule for identifying a leap year is as follows:

    If the year is evenly divisible by 4 and the year is not a century; or the year is a century that is divisible by 400 then the year is a leap year.

This can be expressed as follows:

(((yearNumber%4 == 0) && (yearNumber%100 != 0)) 
        || (yearNumber%400 == 0))

A application program that makes use of the DataValidation class is presented in Table 2. (Note that this example is based on a similar example presented by Holmes, p105.)

// DATE VALIDATION
// Frans Coenen
// Tuesday 16 July 1999
// The University of Liverpool, UK

class DateValidation {

    // ------------------ FIELDS ------------------------
    
    static private final int MIN_MONTH_NUMBER = 1;
    static private final int MAX_MONTH_NUMBER = 12;
    static private final int MIN_DAY_NUMBER = 1;
    private int dayNumber;
    private int monthNumber;
    private int yearNumber;

    // ------------------ CONSTRUCTORS ------------------------
    
    /* ------ DATE VALIDATION ------ */	
	
    public DateValidation(int dateCode) {
        dayNumber = dateCode/1000000;
	monthNumber = (dateCode%1000000)/10000;
	yearNumber = dateCode%10000;
        }
    
    // ------------------ METHODS ------------------------
    
    /* ------- CHECK MONTH ------ */
   
    public boolean monthNumberWithinRange() {
    	if ((monthNumber < MIN_MONTH_NUMBER) || 
				(monthNumber > MAX_MONTH_NUMBER)) {
	    System.out.println("ERROR: " + monthNumber + 
	    			" is an invalid month number");
            return(false);
	    }
	else return(true);
	}

    public boolean dayNumberWithinRange() {
    	if  ((dayNumber < MIN_DAY_NUMBER) || 
				(dayNumber > getNumDaysInMonth())) {
	    System.out.println("ERROR: " + dayNumber + 
	    			" is an invalid day number");
            return(false);
	    }
	else return(true);
	}
    	
    /* ------ NUMBER OF DAYS IN MONTH ------ */
    
    private int getNumDaysInMonth() {
	int numDaysInMonth=0;
	
	switch(monthNumber) {
	    case 1: case 3: case 5: case 7: case 8: case 10: case 12:
	        numDaysInMonth = 31;
	        break;
	    case 4: case 6: case 9: case 11: 
	        numDaysInMonth = 30;
	        break;
	    case 2:
	        // Test for leap year
	        if (((yearNumber%4 == 0) && (yearNumber%100 != 0)) || 
						(yearNumber%400 == 0))
	            numDaysInMonth = 29;   
		else numDaysInMonth = 28;
		break;
	    default:
	    	System.out.println("ERROR: Cause unknown");
            }
	   
	// Return
	
	return(numDaysInMonth); 
	}
    }

Table 1: Date validation class implementation

// DATE VALIDATION APPLICATION
// Frans Coenen
// Wednesday 3 March 1999
// Modified: Saturady 17 September 2005
// University of Liverpool

import java.io.*;

class DateValidationApp {

    // ------------------- FIELDS ------------------------ 
                                
    // Create Scanner class instance
    
    public static Scanner keyboardInput = new Scanner(System.in);
                                         
    // ------------------ METHODS ------------------------  
                                
    /* Main method */
                                
    public static void main(String argv[]) {
	int date;
        DateValidation newDateValidation; 
	                           
        // Input date                                    
	System.out.println("Input a date in DDMMYYYY format");
 	date = keyboardInput.nextInt();
	
	// Create an instance of the class DataValidation	
	newDateValidation = new DateValidation(date);
	
	// Check	
	if (newDateValidation.monthNumberWithinRange()) {
		if (newDateValidation.dayNumberWithinRange())
			System.out.println("Date format OK\n");
		else System.out.println("Date format incorrect\n");
		}
	else System.out.println("Date format incorrect\n"); 
	}
    }

Table 2: Date validation application program


REFERENCE

  1. Holmes, B. (1998). Programming with Java. Jones and Bartlett, Sudbury, Massachusetts.


Created and maintained by Frans Coenen. Last updated 10 February 2015