You want to add a break/new line at the end of your string.
You can find the space via lastIndexOf(), this will give you the int of where the space is located in the String sentence.
You can use this small example here:
public class Main {
public static void main(String[] args) {
String sentence = "I am Mahesh 123";
int locationOfLastSpace = sentence.lastIndexOf(' ');
String result = sentence.substring(0, locationOfLastSpace) //before the last word
+ "\n"
+ sentence.substring(locationOfLastSpace).trim(); //the last word, trim just removes the spaces
System.out.println(result);
}
}
Note that StringBuilder is not used because since Java 1.6 the compiler will create s StringBuilder for you