Java - parse String and add Line break every 100 characters [duplicate]

Answer 1

Quite simply:

StringBuilder sb = new StringBuilder();
for (int i = 0; i < str.length(); i++) {
    if (i > 0 && (i % 100 == 0)) {
        sb.append("\n");
    }

    sb.append(str.charAt(i));
}

str = sb.toString();