Difference between revisions of "Cellphone Texting"

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phone, force the keys 7 and 9 to have four characters each. All other keys have 3
 
phone, force the keys 7 and 9 to have four characters each. All other keys have 3
 
characters.
 
characters.
−
 
+
<br>
 
Write a program which, given a word (a string of upper case letters with no
 
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
 
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
 
multiple times, it should appear that many times in the input. A pause is indicated
 
by a single space.
 
by a single space.
−
 
+
<br>
 
Examples:
 
Examples:
 
{{OutputBlock
 
{{OutputBlock
Line 33: Line 33:
 
This problem will cover the following topics:
 
This problem will cover the following topics:
 
*[[Control_Structures|If and nested if statements]]
 
*[[Control_Structures|If and nested if statements]]
−
*[[Named_Constants|Named constants]]
+
*[[Processing_Arrays_(using for loops)|Arrays]]
 
*[[Input using Scanner|Scanner]]
 
*[[Input using Scanner|Scanner]]
 
*[[Output_using_System.out.|System.out]]
 
*[[Output_using_System.out.|System.out]]
−
<br>
+
*[[Arithmetic_Operators|Modulus]]
−
Example: User inputs "2" for the month and "2004" for the year would result in something like "February 2004 has 29 days."
+
*[[While Loops| While loops]]
−
<br>
+
 
−
<br>
+
  
 
|SideSectionTitle=By Students...
 
|SideSectionTitle=By Students...
  
−
|SideSection=I remember coming into COMP 1010 having taken AP Computer Science in high school. One thing to note is the KISS theory, Keep it Simple Stupid. In other words, don't over complicate the matter where even yourself can't understand your own code looking over it. <br><br>Back in my day it was a bit of a game to try and code the fewest lines as possible, I think now it is more about code readability and code cleanliness, the flow of logic. Does it make sense? Is it readable? Can someone easily follow the thought process? <br><br>You also don't realize how important and how much you will appreciate comments until you have to debug code that has not been commented or that you haven't touched in a while. I used to be lazy to comment one day I was at work and I had to fix a bug in a program that I wrote. It was quite the adventure trying to remember what I was thinking back when I wrote it to which I am now appreciative of comments that people write including my own. Computers are fast these days; one core, two core, three core, and more, and number of lines is a story of the past.
+
|SideSection=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.
−
 
+
 
<BR>
 
<BR>
  
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−
Define your named constants and provide them with appropriate values, in this example there is one constant for 31 days one for 30 days and one for February. You can name them however you want but be sure to declare them as static constants since we are working in static main. Also note that it is declared outside of main, more often named constants are used throughout the java class where multiple functions can access it.  
+
Next is to think all the step necessary for the program to work.<br>
 +
*Get user input
 +
*Check if the input are all numbers or numbers with spaces
 +
*Process the input and change them to letters
 +
{{note}}This solution will show 4 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<br>
 +
 
 +
 
 +
First to get the Input of the user.<br>
 +
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.
 +
 
 
{{CodeBlock
 
{{CodeBlock
 
|Code=
 
|Code=
−
final static int MONTH30 = 30;
+
Scanner scan = new Scanner(System.in); // To enter the input
−
final static int FEB = 28;
+
String input = " ";                     // Store the input
−
final static int MONTH31 = 31;
+
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);
 +
System.out.print("\nEnter code: ");
 +
}
 +
else
 +
{
 +
System.out.println("Invalid Input");
 +
System.out.print("Enter code: ");
 +
}
 +
 
 +
}
 
}}
 
}}
  
  
−
Next define your local variables and initialize them to sentinel values for future error checking described later. We will need a year, monthNum and monthName as defined accordingly.
+
Next define your local variables and initialize them to sentinel values for future error checking described later. You will need a year, monthNum and monthName as defined accordingly.
 
{{CodeBlock
 
{{CodeBlock
 
|Code=
 
|Code=
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else
 
else
 
{
 
{
−
System.out.println("Invalid month number entered, choose between 1 - 12 (Jan - Dec)");
+
System.out.println("Invalid month number entered, choose betyouen 1 - 12 (Jan - Dec)");
 
}
 
}
 
}}
 
}}
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−
Now we 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 were entered for month and year. <br>
+
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.
 
First case, if user left both month and year blank.
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−
Third case, if user entered an invalid year, i.e. negative or in this problem we assume year 1000 is the first year
+
Third case, if user entered an invalid year, i.e. negative or in this problem you assume year 1000 is the first year
 
{{CodeBlock
 
{{CodeBlock
 
|Code=
 
|Code=
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−
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, we will have to separate the conditions into statements. In this problem we separated the months by 31 days, 30 days, and February as a case of its own for calculating leap years.<br>
+
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.<br>
  
−
Months with 31 days, since we 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 we have chosen this method. Lastly, System.out.println prints an meaningful output message.
+
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.
 
{{CodeBlock
 
{{CodeBlock
 
|Code=
 
|Code=
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−
Lastly, for additional robustness, you can check if the user enters a monthNum that is too high. Remember, initially we 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.
+
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.
 
{{CodeBlock
 
{{CodeBlock
 
|Code=
 
|Code=
 
//number is larger than 11
 
//number is larger than 11
 
else
 
else
−
System.out.println("Invalid month number entered, choose between 1 - 12 (Jan - Dec)");
+
System.out.println("Invalid month number entered, choose betyouen 1 - 12 (Jan - Dec)");
 
}}
 
}}
 
{{OutputBlock
 
{{OutputBlock
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Please enter the month [Jan(1) to Dec(12)]: 13
 
Please enter the month [Jan(1) to Dec(12)]: 13
 
Please enter the Year: 2009
 
Please enter the Year: 2009
−
Invalid month number entered, choose between 1 - 12 (Jan - Dec)
+
Invalid month number entered, choose betyouen 1 - 12 (Jan - Dec)
 
}}
 
}}
  
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//number is larger than 11
 
//number is larger than 11
 
else
 
else
−
System.out.println("Invalid month number entered, choose between 1 - 12 (Jan - Dec)");
+
System.out.println("Invalid month number entered, choose betyouen 1 - 12 (Jan - Dec)");
 
}
 
}
 
else
 
else

Revision as of 01:51, 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 62227777444
Translated Code: COMCSI
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 4 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);
		System.out.print("\nEnter code: ");
		}
	else
	{
		System.out.println("Invalid Input");
		System.out.print("Enter code: ");
	}

}


Next define your local variables and initialize them to sentinel values for future error checking described later. You will need a year, monthNum and monthName as defined accordingly. 

 int year, monthNum;
String monthName;
Scanner input = new Scanner(System.in);
	
//sentinel values for error checking 
monthNum = -1;
year = -1;
monthName = "";


Capturing the user input using Scanner and to make sure the user did not enter non-numeric value 

 System.out.print("Please enter the month [Jan(1) to Dec(12)]: ");
if(input.hasNextInt())
{
	monthNum = input.nextInt();

	System.out.print("Please enter the Year: ");
	if(input.hasNextInt())
	{

                //code here

	}
	else
	{
		System.out.println("Please try again, there was an error with the month or the year you have entered");
	}
}
else
{
	System.out.println("Invalid month number entered, choose betyouen 1 - 12 (Jan - Dec)");
} 
 Please enter the month [Jan(1) to Dec(12)]: abcd
Please enter the Year: 2009
Invalid input of month 
 Please enter the month [Jan(1) to Dec(12)]: 12
Please enter the Year: asdf
Invalid Input of Year


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.

First case, if user left both month and year blank. 

 if (monthNum <= 0 && year <= 999)		
	System.out.println("Please try again, there was an error with the month and the year you have entered"); 
 Please enter the month [Jan(1) to Dec(12)]: -1
Please enter the Year: 987
Please try again, there was an error with the month and the year you have entered


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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