4 replies to this topic

[bloodchains]

I'm supposed to compare the end of two strings and see if they are equal. Here's my code:

String a = "s";

String b = "Hellos";

System.out.println(a.toLowerCase().substring(a.length() - 1, a.length()));

System.out.println(b.toLowerCase().substring(b.length() - 1, b.length()));

if (a.toLowerCase().substring(a.length() - 1, a.length()) == b.toLowerCase().substring(b.length() - 1, b.length()))

   System.out.println("true");

else

   System.out.println("false");

I put the two System.out.println at the top to see what comes out. Here, they look like they're equal, but it comes out as "false." What's going on here? It doesn't matter if they're uppercase or lowercase, so I put .toLowerCase on them.

[wim DC]

They are false because you use ' == ' instead of ' .equals(..)'
' == ' will check if their addresses in the memory are equal. equals() checks their value.

Know that strings have an endsWith() method..

[bloodchains]

wim DC said:

They are false because you use ' == ' instead of ' .equals(..)'
' == ' will check if their addresses in the memory are equal. equals() checks their value.

Know that strings have an endsWith() method..

Ahh yes, I totally forgot about .equals(). Anyway, this is a problem from CodingBat website, and I finally got it right, although it's quite lengthy.

public boolean endOther(String a, String b) {
  if (a.length() < b.length() && b.toLowerCase().substring(b.length() - a.length(), b.length()).equals(a.toLowerCase().substring(0, a.length())))
     return true;
  else if (b.length() < a.length() && a.toLowerCase().substring(a.length() - b.length(), a.length()).equals(b.toLowerCase().substring(0, b.length())))
     return true;
  else if (a.length() == b.length() && a.toLowerCase().substring(0, a.length() - 1).equals(b.toLowerCase().substring(0, b.length() - 1)))
     return true;
  else
     return false;
}

If any of you have a simpler solution, please let me know. Oh, and here's the link to the problem:
CodingBat Java String-2 endOther

[wim DC]

What I would do:

public boolean endOther(String a, String b) {

        a = a.toLowerCase();

        b = b.toLowerCase();

        return b.endsWith(a) || a.endsWith(b);

}

You can even put the toLowerCase on the return-line, but I don't like very long lines a lot.

[PhillipKessels]

I know it's cheatin'´, but in a lot of these exercises you could simply use the StringBuilder (have a look here). Internally it does the same as expected from you (string modification via "String"'s own methods).

//Edit: its actually not done by strings own methods, but with the help of an array of chars

Edited by PhillipKessels, 31 March 2011 - 08:02 AM.