how to use replace functionin java code example

Example 1: replace character in string java

String str = ".............................."; 

        int index = 5; 
  
        char ch = '|'; 
 
        StringBuilder string = new StringBuilder(str); 
        string.setCharAt(index, ch); 

        System.out.println(string);

Example 2: how to count an replace substring string in java

String str = "helloslkhellodjladfjhello";
String findStr = "hello";
int lastIndex = 0;
int count = 0;
while(lastIndex != -1){
    lastIndex = str.indexOf(findStr,lastIndex);
    if(lastIndex != -1){
        count ++;
        lastIndex += findStr.length();
    }
}
System.out.println(count);