java中的字符串替换方法问题

Question

My problem is to replace only the last occurrence of a character in the string with another character. When I used the String.replace(char1, char2), it replaces all the occurrences of the character in the string.

For example, I have an address string like

String str = "Addressline1,Addressline2,City,State,Country,"; .

I need to replace the occurrence of ',' at the end of the string with '.'.

My code to replace the character is

str = str.replace(str.charAt(str.lastIndexOf(",")),'.');

After replacing, the string looks like:

Addressline1.Addressline2.City.State.Country.

Is there the problem in Java SDK?. If yes, how to resolve it?

Answer 1

You should use String.replaceAll which use regex

str = str.replaceAll (",$", ".");

The $ mean the end of the String

Answer 2

The Java replace function has a method declaration of:

public String replace(char oldChar, char newChar)

According to the docs replace will:

Return a new string resulting from replacing all occurrences of oldChar in this string with newChar .

So your code:

str.charAt(str.lastIndexOf(","))

Will clearly return the character , . replace will then replace all instances of the oldChar , with the newChar . . This explains the behavior you were seeing.

The solution that @ScaryWombat beat me to is your best option:

str = str.replaceAll(",$", ".");

Since, in regular expression terms, $ denotes the end of a String.

Hope this helps!