java - How to use Caret and dollar in regex Expression? -

i'm trying learn regex i'm struck @ first code only. read caret(^) , dollar($) used match @ beginning , end of test respectively. i'm getting hard time figure out wrong code.

  public class test1 {          public static void main(string[] args) {             // todo auto-generated method stub             string lettera="cat die";             string pattern="[^cat]";             system.out.println(lettera.matches(pattern));             string pattern1="^(cat)";             system.out.println(lettera.matches(pattern1));             string letterb="lending cat";             string pattern3="[cat$]";             system.out.println(letterb.matches(pattern3));             string pattern4="cat$";             system.out.println(letterb.matches(pattern4));         }      } 

every syso giving me output false

caret , dollar anchors tells if pattern should start(caret) , end(dollar) of line.

also, inside of brackets, syntax changed. if start [^...] means negation, trying match char not after caret. , $ inside brackets tells engine looking match $ char.

also, matches in java return true if match entire string.

having things in mind, lets pass each of cases , see why not matching:

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string lettera="cat die"; string pattern="[^cat]"; 

this regex looking single char not 'c' or 'a' or 't'. string "f" return true one.

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system.out.println(lettera.matches(pattern)); string pattern1="^(cat)"; 

the () capturing groups, nothing in case matching. ^ tells match in start of string, , regex trying match string "cat". possible match returns true case.

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string letterb="lending cat"; string pattern3="[cat$]"; 

this trying match single char strings either 'c' or 'a' or 't' or '$'

and :

string pattern4="cat$"; 

is trying match string 'cat' (anchored end, doesn't make difference).

so, problem, need use .* operator matches number of chars like:

• ^cat.*$ (if want string starts cat)
• ^.*cat$ (if want string ends cat)
• ^.*cat.*$ (if want string has text cat in it)