Help with an array

[eric elysia]

Hello,

I am working on an array program. I have some array based questions.

How can I limit the user input to 80? When I run the program it allows me to enter in as many as I want.

Is there a way to know if the user has input symbols instead of letters or numbers?

I am going to break this program up into methods. One method that I will be using is: public static boolean palindrome(char[] a, int used)

Any suggestions are appreciated.
Thanks,
Eric

public class PalindromeCheck
{
public static void main(String[] args)
{
String charString;
char[] a = new char[80];

int used = 0;

//INPUT-------------------------------------------------------------------------
System.out.println("Input a string of characters followed by a period.");
System.out.println("You must make sure that you include the period at the end");
System.out.println("of the string or else you will not get correct results.\n");
charString = SavitchIn.readLine();  

//Make sure the user can only enter 80 char max (79 plus the period).
//if(a.length > 80) ???

//make sure the input is either letters or blank spaces
System.out.println("The length of the string without the period is " + (charString.length()-1));

char input[] = charString.toCharArray();
for(int i = 0; i < (input.length); i++)
{
if(Character.isLetter(input[i]) || Character.isSpaceChar(input[i]))
{
//Maybe check for numbers instead so the if statement isn't empty.  What about symbols?
}
else
System.out.println("The input must be a letter or a white space.");
break;
}

a = charString.toUpperCase().toCharArray(); //toCharArray() converts a string to an array of characters

for(int i = 0; i < a.length; i++)//displays the array to the screen
{
System.out.print(a[i]);
}
System.out.println("Is this the correct string of characters?");
//if(


for(int i = 0; i < a.length; i++)//increments int used
{
used++;
}

System.out.println("\nThe number of indexes already used is " + used + ".");//displays the number of indexes already used

System.out.println("The lowest index used is index a[0].\n");//displays the lowest index

System.out.println("The highest index used is index a[" + (a.length-1) + "].");//displays the highest index used
//----------------------------------------------------------------------------------


//ACTION----------------------------------------------------------------------------
//check for palindrome
int left = 0;
int right = a.length - 2;  // Subtract 2 from length, one for index 0 and one for the period
boolean charsMatch = true;

while(left <= right && charsMatch)//compare characters in the characterString
{
if(a[left] == a[right])
{
left++;
right--;
}
else
{
charsMatch = false;
}
}
//RESULTS------------------------------------------------------------------------
//display charString and palindrome check results
if(charsMatch)
{
System.out.println(charString + " \nIS A PALINDROME.\n");
}
else

System.out.println(charString + " \nIS NOT A PALINDROME.\n");

//write a loop that checks additional strings until the user requests that the program ends.
}
}

[Marilyn de Queiroz]

Do you want to do something when the user reaches 80 or do you just want to chop off any characters that are entered after that?

What kind of symbols did you have in mind? A '?', a '$', a '*', a '-' or anything other than a letter, number or whitespace??

[eric elysia]

I just want to be able to make sure the user did not enter more than 80 characters (including the period).

I meant these symbols: @, #, $, etc.

I guess I also need to convert the input to uppercase.

Thank you,
Eric

[eric elysia]

OK, I have started to clean it up a little bit. Here is what I now have. I am not sure how to use the method:

public static boolean palindrome(char[]a, int used)

to keep track of how much of the array is used.

Any help is appreciated!
Thanks,
Eric

public class PalindromeCheck
{
String charString;
char[] a = new char[80];
int used = 0;

//INPUT-------------------------------------------------------------------------
public void getInput()
{
System.out.println("Input a string of characters followed by a period.");
System.out.println("You must make sure that you include the period at the end");
System.out.println("of the string or else you will not get correct results.\n");
charString = SavitchIn.readLine();  

//Make sure the user can only enter 80 char max (79 plus the period).
//if(a.length > 80) ???

//Make sure to ignore case when comparing letters

//make sure the input is either letters or blank spaces

char input[] = charString.toCharArray();
for(int i = 0; i < (input.length); i++)
{
if(Character.isLetter(input[i]) || Character.isSpaceChar(input[i]))
{
//Maybe check for numbers instead so the if statement isn't empty.  What about symbols?
}
else
System.out.println("The input must be a letter or a white space.");
break;
}

a = charString.toUpperCase().toCharArray(); //toCharArray() converts a string to an array of characters

System.out.println("\nThe string of characters you entered is: ");
for(int i = 0; i < a.length; i++)//displays the array to the screen
{
System.out.print(a[i]);
}
System.out.println("\nIs this the correct string of characters?");
//if(

for(int i = 0; i < a.length; i++)//increments int used
{
used++;
}

System.out.println("\nThe length of the string without the period is " + (charString.length()-1));
System.out.println("The number of indexes already used is " + used + ".");//displays the number of indexes already used
System.out.println("The lowest index used is index a[0].");//displays the lowest index
System.out.println("The highest index used is index a[" + (a.length-1) + "].");//displays the highest index used
}//----------------------------------------------------------------------------------


//---------------------------------------------------------------------------------
/***
I MUST USE THIS METHOD:
//Precondition:  The array a contains letters and blanks in positions a[0] through a[used-1].
//Returns true if the string is a palindrome and false otherwise.

//public static boolean palindrome(char[] a, int used)

//The program will call the preceding method with the array and one other int variable.  
//The other int variable keeps track of how much of the array is used (partially filled array).

***/
//----------------------------------------------------------------------------------


//ACTION----------------------------------------------------------------------------
public void checkInput()//check for palindrome
{
int left = 0;
int right = a.length - 2;  // Subtract 2 from length, one for index 0 and one for the period
boolean charsMatch = true;

while(left <= right && charsMatch)//compare characters in the characterString
{
if(a[left] == a[right])//!!!Make sure to ignore case when comparing letters!!!
{
left++;
right--;
}
else
{
charsMatch = false;
}
}
//RESULTS------------------------------------------------------------------------
//display charString and palindrome check results
if(charsMatch)
{
System.out.println("\n\n" + charString + " \nIS A PALINDROME.\n");
}
else
System.out.println("\n\n" + charString + " \nIS NOT A PALINDROME.\n");

//write a loop that checks additional strings until the user requests that the program ends.
}

//MAIN--------------------------------------------------------------------------------------
public static void main(String[] args)
{
PalindromeCheck checkIt = new PalindromeCheck();
checkIt.getInput();
checkIt.checkInput();
//checkIt.giveOutput();
}

}

[David Harkness]

You had the solution in your original post:

System.out.println("The length of the string without the period is " 
                   + (charString.length()-1));

What do you want your program to do if the user enters more than 80 characters: let them try again or exit?