[2019.11.27] learning algorithm of record --IP address is invalid

The so-called IP address invalidation, in fact, is to use "[.]" Instead of each. "."

Example 1:

Input: address = "1.1.1.1"
Output: "[.] [.] [.] 1 1 1 1"
Example 2:

Input: address = "255.100.50.0"
Output: "[.] [.] [.] 255100500"

prompt:

given address is a valid IPv4 address

Source: stay button (LeetCode)

class Solution {
    public String defangIPaddr(String address) {
        char[] old = address.toCharArray();
        String newAdd = "";
        for(int i = 0; i<old.length; i++){
            if(old[i] != '.'){
                newAdd = newAdd + old[i];
            }
            else{
                newAdd = newAdd + "[.]";
            }
        }
        return newAdd;
    }
}

Note
one of a character string is replaced with a method of another character:

String old = "Hello";
String newWord;
newWord = old.replace('l','w');

The above code output is "Hewwo"