Answer 1

public class Program
{
public static void main(String[] args)
{

String input = "Hello World!.";

System.out.println("Convert to uppercase:" + input.toUpperCase());
System.out.println("Convert to lowercase:" + input.toLowerCase());
System.out.println("Toggle to :" + toggleString(input));

}

public static String toggleString(String input)
{
String result = "";
for(int i=0; i<input.length(); i++)
{

char letter = input.charAt(i);

if(Character.isUpperCase(input.charAt(i)))
{
letter = Character.toLowerCase(letter);
result = result + letter;

}
else if(Character.isLowerCase(input.charAt(i)))
{
letter = Character.toUpperCase(letter);
result = result + letter;
}
else {
result = result + letter;
}

}
return result;

}
}