How do you Reverse String in java public class StringPrograms { public static void main(String[] args) { String str = "123"; System.out.println(reverse(str)); } public static String reverse(String in) { if (in == null) throw new IllegalArgumentException("Null is not valid input"); StringBuilder out = new StringBuilder(); char[] chars = in.toCharArray(); for (int i = chars.length - 1; i >= 0; i--) out.append(chars[i]); return out.toString(); } } —----------------Swap 2 number without using 3 variable public class SwapNumbers { public static void main(String[] args) { int a = 10; int b = 20;     System.out.println("a is " + a + " and b is " + b); a = a + b; b = a - b; a = a - b;     System.out.println("After swapping, a is " + a + " and b is " + b);     } } —-------------------check if vowel is present in string public class StringContainsVowels { public static void ...