Difference between revisions of "Cellphone Texting"

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Line 127: Line 127:
 
{{CodeBlock
 
{{CodeBlock
 
|Code=
 
|Code=
−
String output = "";            //Store each number that is translated into letter
+
public static String codeEncription(String input)
−
int counter = 1;                //count the number of same consecutive number
+
−
char last = input.charAt(0);    //Initialize the last to the first character of the string
+
−
char cur = input.charAt(0);    //Initialize the cur to the first character of the string
+
−
for(int i = 1 ; i <= input.length();i++)
+
 
{
 
{
−
if(i < input.length())            
+
String output = "";            //Store each number that is translated into letter
 +
int counter = 1;                //count the number of same consecutive number
 +
char last = input.charAt(0);    //Initialize the last to the first character of the string
 +
char cur = input.charAt(0);    //Initialize the cur to the first character of the string
 +
for(int i = 1 ; i <= input.length();i++)
 
{
 
{
−
cur = input.charAt(i);    //store the current character to cur
+
if(i < input.length())           
−
}
+
{
−
else
+
cur = input.charAt(i);    //store the current character to cur
−
{
+
}
−
cur = '.';                  //this else statement is necessary to complete the last letter of the input
+
else
−
}
+
{
 +
cur = '.';                  //this else statement is necessary to complete the last letter of the input
 +
}
  
−
if(cur == last)
+
if(cur == last)
−
{
+
{
−
counter++;                  //number of same consecutive number
+
counter++;                  //number of same consecutive number
−
}
+
}
−
else
+
else
−
{
+
{
  
−
output += converter(last,counter) +"";  //this will call converter() method that will change the number into letter
+
output += converter(last,counter) +"";  //this will call converter() method that will change the number into letter
−
last = cur;                            //to set the last into the current character
+
last = cur;                            //to set the last into the current character
−
counter = 1;
+
counter = 1;
 +
}
 
}
 
}
 +
return output;                                          // return the translated code
 
}
 
}
−
return output;                                          // return the translated code
 
−
 
 
}}
 
}}
−
\
 
  
−
Now you have to break up the problem into a series of cases and separate the conditions into if statements. The first 3 if statements is for error checking and validate the user input to make sure valid numbers youre entered for month and year. <br>
 
  
−
First case, if user left both month and year blank.
+
Last step is to make a method that will convert the number into letter using String array and Modulus.<br>
 +
In this method, there are two parameter ,char and int, the char represent the number and the in represent how many consecutive number was found in the current search from the other method. This will return the equivalent letter or if its space it will return empty String.  
 
{{CodeBlock
 
{{CodeBlock
 
|Code=
 
|Code=
−
if (monthNum <= 0 && year <= 999)
+
public static String converter(char find,int count)
−
System.out.println("Please try again, there was an error with the month and the year you have entered");
+
{
−
}}
+
        //String array are manually entered. The arrangement of letters is necessary in order to get the right letter
−
{{OutputBlock
+
String[] two = {"C","A","B"};
−
|Code=
+
String[] three = {"F","E","D"};
−
Please enter the month [Jan(1) to Dec(12)]: -1
+
String[] four = {"I","G","H"};
−
Please enter the Year: 987
+
String[] five = {"L","J","K"};
−
Please try again, there was an error with the month and the year you have entered
+
String[] six = {"O","M","N"};
 +
String[] seven = {"S","P","Q","R"};
 +
String[] eight = {"V","T","U"};
 +
String[] nine = {"Z","W","X","Y"};
 +
String convert = "";
 +
 
 +
        //doing a modulus will return either 1,2 or 0 if its mod 3 and 1,2,3 or 0 if its mod 4
 +
if(find == '2'){
 +
convert = two[(count%3)];
 +
}else if(find == '3')
 +
{
 +
convert = three[(count%3)];
 +
}else if(find == '4')
 +
{
 +
convert = four[(count%3)];
 +
}else if(find == '5')
 +
{
 +
convert = five[(count%3)];
 +
}else if(find == '6')
 +
{
 +
convert = six[(count%3)];
 +
}else if(find == '7')
 +
{
 +
convert = seven[(count%4)];
 +
}else if(find == '8')
 +
{
 +
convert = eight[(count%3)];
 +
}else if(find == '9')
 +
{
 +
convert = nine[(count%4)];
 +
}
 +
 
 +
return convert;
 +
}
 
}}
 
}}
  

Revision as of 05:01, 5 December 2011

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Problem

In non-smart cell phones, text input can be handled by a technique called multi-tap(example picture: link here). With multi-tap, you use the letters on each key, and press a key multiple times to access different letters. For instance, to get the letter 'a', you press the 2 key once, but to get 'n', you press the 6 key twice (the first press gives you 'm', the second switches 'm' to 'n'). A slight pause by the user will indicate the end of inputting one character and a beginning of the input of the next character. The letters 'q' and 'z', not originally part of the letters on a phone, force the keys 7 and 9 to have four characters each. All other keys have 3 characters.
Write a program which, given a word (a string of upper case letters with no spaces), outputs the sequence of keystrokes using multi-tap. If a key is pressed multiple times, it should appear that many times in the input. A pause is indicated by a single space.
Examples: 

 Enter code: 222666 67777222444
Translated Code: COMSCI
Enter code: 7 2 777 2 7777 444 8 444 222
Translated Code: PARASITIC


This problem will cover the following topics:

 

By Students...

COMP 1010 is where I first learned how to make a program. I was only taking that course for prerequisite and do not have interest on it, but as time goes by, I notice that I was enjoying myself making a program.

Solution

Start by importing the swing java package. 

 import javax.swing.*;
import java.util.Scanner;


Next is to think all the step necessary for the program to work.

  • Get user input
  • Check if the input are all numbers or numbers with spaces
  • Process the input and change them to letters

Note Note: This solution will show 3 method to do all these steps to make the program look neat. You can always put all codes in main but it will be messy


First to get the Input of the user.
In order to get the user input, you have to use the Scanner's method .nextLine() in order to get the whole input. Since you do not know the when user will stop, you have to put the scanner inside a while loop. You also want to check validation of the input but let another method handle the validation. If input is not valid, output an error message to alert the user. 

 Scanner scan = new Scanner(System.in);  // To enter the input
String input = " ";                     // Store the input
String convert = "";	                // Store the translated input
System.out.print("Enter code: ");

while(!input.equals(""))
{
	input = scan.nextLine();         // scan will get the user input and store in in the String input

	if(checkInput(input))            // calls the method checkInput to check for validation
	{
		convert = codeEncription(input);                 //calls the method codeEcription to translate the input into letters
		System.out.print("Translated Code: "+convert);   //output message
		System.out.print("\nEnter code: ");
		}
	else
	{
		System.out.println("Invalid Input");              //error message
		System.out.print("Enter code: ");
	}

} 
 Enter code: 23a43
Invalid Input
Enter code: 77 88 444 9999 9999 444 222 2 555
Translated Code: QUIZZICAL


Next is to make a method that will validate the user input.It will have a String as a parameter to pass the input to this method
You have to check each character in the input to see if there is an invalid input. While loops is still necessary for this task since you don't know if you will find an error or not in the input. This method will return true if its valid or false if invalid. 

 public static boolean checkInput(String input)
{
	boolean check = true;
	int counter = 0;

	while( check && counter < input.length())  
	{
		if(input.charAt(counter) == ' ')        //if space is found in the input its still valid
			counter++;
		else if(input.charAt(counter) < '0' || input.charAt(counter) > '9')  //check if its a number or not
			check = false;
		else
			counter++;
	}

	return check;     //returns true if valid or false if not valid
}


Next step is to make a method that will translate the input.It has String as a parameter as well.
In order to translate the input, you have to check each character in the String. This means you can use for loops in this method since you will know went exactly to stop. Every time you check a character, store the current character and count how many are there after the current character change. Then pass the current character and the number of count you had to another method what will change the number into Letters 

 public static String codeEncription(String input)
{
	String output = "";             //Store each number that is translated into letter
	int counter = 1;                //count the number of same consecutive number
	char last = input.charAt(0);    //Initialize the last to the first character of the string
	char cur = input.charAt(0);     //Initialize the cur to the first character of the string
	for(int i = 1 ; i <= input.length();i++)
	{
		if(i < input.length())             
		{
			cur = input.charAt(i);     //store the current character to cur
		}
		else
		{
			cur = '.';                  //this else statement is necessary to complete the last letter of the input
		}

		if(cur == last)
		{
			counter++;                   //number of same consecutive number
		}
		else
		{

			output += converter(last,counter) +"";  //this will call converter() method that will change the number into letter
			last = cur;                             //to set the last into the current character
			counter = 1;
		}
	}
	return output;                                           // return the translated code
}


Last step is to make a method that will convert the number into letter using String array and Modulus.
In this method, there are two parameter ,char and int, the char represent the number and the in represent how many consecutive number was found in the current search from the other method. This will return the equivalent letter or if its space it will return empty String. 

 public static String converter(char find,int count)
{
        //String array are manually entered. The arrangement of letters is necessary in order to get the right letter
	String[] two = {"C","A","B"};
	String[] three = {"F","E","D"};
	String[] four = {"I","G","H"};
	String[] five = {"L","J","K"};
	String[] six = {"O","M","N"};
	String[] seven = {"S","P","Q","R"};
	String[] eight = {"V","T","U"};
	String[] nine = {"Z","W","X","Y"};
	String convert = "";

        //doing a modulus will return either 1,2 or 0 if its mod 3 and 1,2,3 or 0 if its mod 4
	if(find == '2'){
		convert = two[(count%3)];
	}else if(find == '3')
	{
		convert = three[(count%3)];
	}else if(find == '4')
	{
		convert = four[(count%3)];
	}else if(find == '5')
	{
		convert = five[(count%3)];
	}else if(find == '6')
	{
		convert = six[(count%3)];
	}else if(find == '7')
	{
		convert = seven[(count%4)];
	}else if(find == '8')
	{
		convert = eight[(count%3)];
	}else if(find == '9')
	{
		convert = nine[(count%4)];
	}

	return convert;
}


Second case, if user entered an invalid monthNumber like a negative month number 

 else if (monthNum <= 0)
{
	System.out.println("Please try again, there was an error with the month you have entered");	
} 
 Please enter the month [Jan(1) to Dec(12)]: -1
Please enter the Year: 2009
Please try again, there was an error with the month you have entered


Third case, if user entered an invalid year, i.e. negative or in this problem you assume year 1000 is the first year 

 else if (year <= 999)
{
	System.out.println("Please try again, there was an error with the month you have entered");	
} 
 Please enter the month [Jan(1) to Dec(12)]: 12
Please enter the Year: 987
Please try again, there was an error with the month you have entered


The last case, which is most important since it is processing the valid input will be the next step. In this case there is a set of nested cases. Again, you will have to separate the conditions into statements. In this problem you separated the months by 31 days, 30 days, and February as a case of its own for calculating leap years.

Months with 31 days, since you are assuming Jan = 0, the condition will "or" all integer representations of the months with 31 days. Remember July and August are back to back months with 31 days! The first condition checks for the appropriate monthNum and the nested conditions will assign the appropriate monthName depending on which integer was chosen. There may be alternate solutions and methods to solve this problem but for the sake of example and topics to cover you have chosen this method. Lastly, System.out.println prints an meaningful output message. 

 //JAN //MAR //MAY //JUL //AUG //OCT //DEC
if (monthNum == 1 || monthNum == 3 || monthNum == 5 || 
	monthNum == 7 || monthNum == 8 || monthNum == 10 ||
	monthNum == 12)
{
	if (monthNum == 1)
		monthName = "January";
	else if (monthNum == 3)
		monthName = "March";
	else if (monthNum == 5)
		monthName = "May";
	else if (monthNum == 7)
		monthName = "July";
	else if (monthNum == 8)
		monthName = "August";
	else if (monthNum == 10)
		monthName = "October";
	else if (monthNum == 12)
		monthName = "December";
		
	System.out.println(monthName + " " + year + " has " + MONTH31 + " days.");
} 
 Please enter the month [Jan(1) to Dec(12)]: 3
Please enter the Year: 2009
March 2009 has 31 days.


The case of February checks if monthNum = 1 but for the nested conditions, it checks if the year is divisible by 4 by using the mod operator. If it is in fact a leap year, 1 is added to the constant. 

 //FEB
else if (monthNum == 2)
{
	monthName = "February";

	//check for leap
	if (year % 4 == 0)
		System.out.println(monthName + " " + year + " has " + (FEB + 1) + " days.");
	else
		System.out.println(monthName + " " + year + " has " + FEB + " days.");				
} 
 Please enter the month [Jan(1) to Dec(12)]: 2
Please enter the Year: 2008
February 2009 has 29 days. 
 Please enter the month [Jan(1) to Dec(12)]: 2
Please enter the Year: 2009
February 2009 has 28 days.


Months with 30 days are the last group of valid inputs to check. Similar to the months with 31 days, the first condition checks for an appropriate monthNum and the nested condition assigns the appropriate monthName. 

 //APR //JUN //SEP //NOV
else if (monthNum == 4|| monthNum == 6 || monthNum == 9 || monthNum == 11)
{
	if (monthNum == 4)
		monthName = "April";
	else if (monthNum == 6)
		monthName = "June";
	else if (monthNum == 9)
		monthName = "September";
	else if (monthNum == 11)
		monthName = "November";
			
	System.out.println(monthName + " " + year + " has " + MONTH30 + " days.");
} 
 Please enter the month [Jan(1) to Dec(12)]: 11
Please enter the Year: 2009
November 2009 has 30 days.


Lastly, for additional robustness, you can check if the user enters a monthNum that is too high. Remember, initially you checked for negative monthNum, but this time is now the opposite end of the spectrum where the monthNum is too beyond the scope. If the monthNum is too high output a meaningful error message. 

 //number is larger than 11
else
	System.out.println("Invalid month number entered, choose betyouen 1 - 12 (Jan - Dec)"); 
 Please enter the month [Jan(1) to Dec(12)]: 13
Please enter the Year: 2009
Invalid month number entered, choose betyouen 1 - 12 (Jan - Dec)


This concludes the program, compile and run.

Code

Solution Code

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