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Java Forum / General / January 2006char cannot be dereferenced
Hello Ik get an error on this piece of code: if((word.charAt(i)).equals("a"){ .... } Error: char cannot be dereferenced Can someone tell me what's wrong? Or how can I compare each letter of the word to the "a"? Thanks > Hello > [quoted text clipped - 10 lines] > > Thanks Try .equals('a'){ becomes == 'a'){ James >> if((word.charAt(i)).equals("a"){ You have two problems. equals is for comparing objects; == is for comparing primitives. You have primitives. Secondly your () don't balance.  SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > Hello > [quoted text clipped - 5 lines] > > Error: char cannot be dereferenced word.charAt(i) returns a char primitive, you can not call methods on a primitive ie equals(String str) For that matter you must make the two objects of the same type to make equals meaningful. so objectOneOfTypeA.equals(objectTwoOfTypeA) // is okay to modify your example char chrPrim = word.charAt(i); Character chrObject = Character.valueOf(chrPrim); boolean isEqual = Character.valueOf('a').equals(chrObject); but since you have a primitive it is easier to just do if ( word.charAt(i) == 'a' ) {...} // !! -- Mike W "VisionSet" <spam@ntlworld.com> wrote in news:WOUwf.32187$yu.5572 @newsfe6-gui.ntli.net: > word.charAt(i) returns a char primitive, you can not call methods on a > primitive ie equals(String str) [quoted text clipped - 14 lines] > > if ( word.charAt(i) == 'a' ) {...} // !! Thanks And if I want to compare a string of vouwels String [] vouwels = {"A", "a", "E", "e", "U", "u", "I", "i", "O", "o"}; if(word.charAt(i) == vouwels[j]){} //? So I need to count the vouwels in a word... > "VisionSet" <spam@ntlworld.com> wrote in news:WOUwf.32187$yu.5572 > @newsfe6-gui.ntli.net: [quoted text clipped - 29 lines] > > So I need to count the vouwels in a word... With proper looping and counting that could do it, yes. Take a look at .toCharArray() method of string, to save repeatedly extracting the same characters out of the string, then it's just a case of looping over the two arrays and incrementing a count when the values match. James >> "VisionSet" <spam@ntlworld.com> wrote in news:WOUwf.32187$yu.5572 >> @newsfe6-gui.ntli.net: [quoted text clipped - 34 lines] > > James As Roedy pointed out you need a char[] not String[] of vowels. This applies to this method as well. James >String [] vouwels = {"A", "a", "E", "e", "U", "u", "I", "i", "O", "o"}; > >if(word.charAt(i) == vouwels[j]){} //? You would need a nested loop over the chars in word and the possible vowels and increment a counter when you find a match. The for:each is neat for this: for ( char vowel : vowels ) But you need to use a char[] instead of a String[]. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. >>String [] vouwels = {"A", "a", "E", "e", "U", "u", "I", "i", "O", "o"}; >> [quoted text clipped - 8 lines] > > But you need to use a char[] instead of a String[]. Simpler, though is: int index = "AaEeIiOoUu".indexOf (word.charAt(i)); if (index >= 0) ... > And if I want to compare a string of vouwels > [quoted text clipped - 3 lines] > > So I need to count the vouwels in a word... The compiler will give an error, because you try to compare char with String. What you probably want to compare char wit char: char [] vouwels = {'A', 'a', 'E', 'e', 'U', 'u', 'I', 'i', 'O', 'o'}; if(word.charAt(i) == vouwels[j]){} Signature"TFritsch$t-online:de".replace(':','.').replace('$','@') >>And if I want to compare a string of vouwels >> [quoted text clipped - 9 lines] > What you probably want to compare char wit char: > char [] vouwels = {'A', 'a', 'E', 'e', 'U', 'u', 'I', 'i', 'O', 'o'}; Or, easier to read: char[] vowels = "AaEeIiOoUu".toCharArray(); Tom Hawtin SignatureUnemployed English Java programmer http://jroller.com/page/tackline/ > Hello > [quoted text clipped - 10 lines] > > Thanks Seems that charAt() returns a char. A char does not have a method named equals. Try if (word.charAt(i) == 'a') { ... } On Tue, 10 Jan 2006 21:54:09 +0100, Malte Christensen <You_can_spam_me_here@nmalte.dk> wrote, quoted or indirectly quoted someone who said : >Seems that charAt() returns a char. A char does not have a method named >equals. In fact, because char is a primitive, it does not have ANY methods. Only Objects have methods, e.g. Character or String. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > On Tue, 10 Jan 2006 21:54:09 +0100, Malte Christensen > <You_can_spam_me_here@nmalte.dk> wrote, quoted or indirectly quoted [quoted text clipped - 5 lines] > In fact, because char is a primitive, it does not have ANY methods. > Only Objects have methods, e.g. Character or String. Tnx for stating the obvious, I had left it to the OP. It sounds like you may even want to look at regular expressions to do your test... >if((word.charAt(i)).equals("a"){ compare Strings with Strings and chars with chars. You have char on the left and String on the right. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Free MagazinesGet these publications absolutely FREE for up to 12 months. 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