i want to replace a word in string by other word
how do this simply ?

If you want to replace all the occurrences of the word take a look at the replaceAll method, else if you would just want to replace the first occurrence of it, use the replaceFirst method. If you still want to do something else, such as replace an occurrence of the word after an occurrence of something else, wellm I have sited here the docs for the String class you can have a look at all the methods it has to offer and decide which suits you best or you could use a few of them in combination to get the desired outcome.

thanks to u i found it