import java.util.Scanner;
public class Palindrome
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.print("Enter a potential palindrome: ");
String palin = scan.nextLine();
String result = "";
for (int count = palin.length()-1; count >= 0; count--)
{
//Need help here
//I want to append to the result String whichever char
//is at palin.charAt(count)
}
}
}
[java] Adding a char to a String?
Author
I'm working on a program to see if a word is a palindrome or not for AP Computer Science.
Now, here's how the program will work generally.
So that's what it'll be doing. However, how do I append a char data type to a String object? I want to then just compare the strings to see if they are the same or not.
Any help please?
Thanks.
This says that you can create a string object from a single character and concatenate two strings (producing a new object - strings are immutable).
Author
Aha, thanks a bunch. I successfully got it working.
Here's how it goes now:
Thanks for the help!
Here's how it goes now:
import java.util.Scanner;public class Palindrome{ public static void main(String[] args) { Scanner scan = new Scanner(System.in); System.out.print("Enter a potential palindrome: "); String palin = scan.nextLine(); String result = ""; for (int count = palin.length()-1; count >= 0; count--) { char current[] = {palin.charAt(count)}; String toConcat = new String(current); result = result.concat(toConcat); } palin = palin.toLowerCase(); result = result.toLowerCase(); System.out.println("\nYour word is: " + palin); System.out.println("Backwards, this is: " + result); if (palin.equals(result)) { System.out.println(); System.out.println("That word is a palindrome!"); } else { System.out.println(); System.out.println("That word is not a palindrome."); } }}Thanks for the help!
You could use StringBuffer and the append() method. Then just do a toString() on the buffer when it's time to compare
Cheers,
Brett
Cheers,
Brett
Strings in Java are immutable; code such as String1 + String2 will compile into byte code that uses StringBuffer to do the concatenation :)
Quote:Original post by Thygrrr
Strings in Java are immutable; code such as String1 + String2 will compile into byte code that uses StringBuffer to do the concatenation :)
That is not guaranteed, just compare the performance and you will note that the second loop takes much longer:
StringBuilder sb = new StringBuilder();for(int i=0; i<15000; i++) sb.append(i); System.out.println(sb); String s = "";for(int i=0; i<15000; i++) s += i;System.out.println(s);Not using a StringBuilder/StringBuffer creates a new Object (String) every concateation, otherwise only when the char array buffer it is newly allocated.
A genral rule is: For few concateations or more with very short arguments the '+' operator is better, otherwise a StringBuilder/StringBuffer should be preferred. (Beside the fact that the latter one can handle char manipulation).
(Side Note: StringBuilder is a non-synchronized version of StringBuffer and potentially more performant, just if anyone is wondering)
This topic is closed to new replies.
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