The method replaceVariables(String) is undefined for the type

I get this message for as many times as I have used replaceVariables in my code. I have added the referenced libraries, but I don't know what else to do. Can someone please help me?

Update: This is the code:

   int k = 0;
for(Xml reg_is:fetchsite.child("site").child("regexps").children开发者_如何学Go("reg"))    
{
if(reg_is.string("name").contains("unique")){


if(reg_is.child("start").content()=="")
    error += "\tNo prefix reg.exp. given.\n";

  else
prefix = HtmlMethods.removeBreaks(replaceVariables(reg_is.child("start").content()));                       

if(reg_is.child("end").content()=="")
    error += "\tNo suffix reg.exp. given.\n";
 else
suffix = HtmlMethods.removeBreaks(replaceVariables(reg_is.child("end").content()));

}
else{
  poleis[k][0]= HtmlMethods.removeBreaks(reg_is.string("name"));
  poleis[k][1] = HtmlMethods.removeBreaks(replaceVariables(reg_is.child("start").content()));//ιδια δομη για ολες τις πολεις
  poleis[k][2] = HtmlMethods.removeBreaks(replaceVariables(reg_is.child("end").content()));
  k++;
 }
}

In this part I use my XML in order to find the data from a HTML page that I want.

---

So, replaceVariables needs to be either a method which is declared in the same class, or it needs to be a static method which is imported using import static. Since it seems to be a method of the HtmlMethods class, my bet is that adding the following line to the imports should fix the problem:

import static com.example.HtmlMethods.*;

You only need to substitute com.example with the actual package name. Another way is to use HtmlMethods.replaceVariables(x) in your code instead.

---

That said, doing a string == "" is not the way to determine if the string equals an empty string. You should use either

if (string.equals("")) {}

or

if (string.length() == 0) {}

or

if (string.isEmpty()) {}

instead. Be aware that string is supposed to be non-null here, else you need to add a string != null as well or to use "".equals(string).

---

On == on reference types

someString == "" is almost always wrong. == is a reference identity comparison. If you want value comparison, use equals. In this particular case, you can use either someString.length() == 0 or someString.isEmpty()

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On += on String

Be aware that this performs quite horribly (quadratic) with really long strings. If you're doing this in a any sizable loop, you'd definitely see the effect. It'd be better to use a StringBuilder.

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