public static void main(String args[]){
String s1="my name is khan my name is java";
String replaceString=s1.replace("is","was");//replaces all occurrences of "is" to "was"
System.out.println(replaceString);
}} 

String str = ".............................."; int index = 5; char ch = '|'; StringBuilder string = new StringBuilder(str); string.setCharAt(index, ch); System.out.println(string); 

function replaceAt(index, word, replacement)
{
let partOne = word.substring(0, index)
let partTwo = word.substring(index, word.length-1);
let answer = partOne + replacement + partTwo;
return answer;
}
var s = new String("AAAAA");
for(var i =0; i<s.length; i++)
{ if(s[i]=="A") {
s= replaceAt(i, s, "@@@@"); }
}
console.log(s);
/*console.log() @@@@@@@@@@@@@@@@@@@@*/

theSTRINGhere.replace('what you want to replace', '');