java - How to replace all chars in the string except another string in this string

Question

For example I have two strings

String a="aaabbbaaa";
String b="bbb";

I need to replace all chars in string a except String b

I need next result (for example we replace all "a" chars with "+"): +++bbb+++

Answer 1

String a="aaabbbaaa";
String b="bbb";


String newA = "";
int i = 0;
while (i < a.indexOf(b)) {
  newA += "+";
  i++;
}

newA +=b;

i = a.lastIndexOf(b);
while (i < a.length()) {
  newA += "+";
  i++;
}
System.out.println(newA);