How to take first half of String and reverse it and combine it with second half. Otherwise Swap the-CodePudding

If length is divisible by two, take first half of String and reverse it and combine with second half. Otherwise Swap first letter to the last letter of the string.

 String[] items = {"milk", "donut", "cookies", "cheese"};
    System.out.println("Original word:\n1.milk\n2.donut\n3.cookies\n4.cheese")

    if (items[0].length() % 2 == 0) //so far I only managed to figure out the divisible.
      {
        //Take first half of String and reverse it and combine with second half
      }
      else
      {
        //Swap first letter to the last letter of the string
      }

    /* Output
    Original word:
    1.milk
    2.donut
    3.cookies
    4.cheese
    Divisible by two: imlk ehcese
    Not Divisible by two: tonud sookiec*/

CodePudding user response：

Hope this code helps you.

public class JavaMain {
    public static void main(String[] args) {
        String[] items = {"milk", "donut", "cookies", "cheese"};

        Arrays.stream(items).forEach(System.out::println);

        List<String> divByTwo    = new ArrayList<>();
        List<String> nonDivByTwo = new ArrayList<>();

        for(String item : items){
            if (item.length() % 2 == 0) {
                divByTwo.add(reverseFirstAndCombineWithSecHalf(item));
                //so far I only managed to figure out the divisible.
                //Take first half of String and reverse it and combine with second half
            } else {
                //Swap first letter to the last letter of the string
                nonDivByTwo.add(String.valueOf(swapFunction(item, 0, item.length()-1)));
            }
        }

        System.out.println("Divisible by two: "   divByTwo.stream().collect(Collectors.joining(" ")));
        System.out.println("Not Divisible by two: "   nonDivByTwo.stream().collect(Collectors.joining(" ")));
    }

    static char[] swapFunction(String item, int from, int to){
        char ch[] = item.toCharArray();
        char temp = ch[from];
        ch[from] = ch[to];
        ch[to] = temp;
        return ch;
    }

    static String reverseFirstAndCombineWithSecHalf(String item){
        String firstHalf  = StringUtils.reverse(StringUtils.substring(item, 0, item.length() / 2));
        String secondHalf = StringUtils.substring(item, item.length() / 2, item.length());
        return firstHalf.concat(secondHalf);
    }
}

Output would be

milk
donut
cookies
cheese
Divisible by two: imlk ehcese
Not Divisible by two: tonud sookiec

CodePudding user response：

Using String and StringBuilder class methods you can do it as below:-

import java.util.Arrays;

public class Test {

    public static void main(String[] args) {
        String[] items = { "milk", "donut", "cookies", "cheese" };
        System.out.println(Arrays.toString(items));

        for (int i = 0; i < items.length; i  ) {
            String item = items[i];
            if (item.length() % 2 == 0) {
                // Take first half of String and reverse it and combine with second half
                StringBuilder firstHalf = new StringBuilder(item.substring(0, item.length() / 2));
                firstHalf = firstHalf.reverse();
                StringBuilder secondHalf = new StringBuilder(item.substring(item.length() / 2));
                items[i] = firstHalf.append(secondHalf).toString();
            } else {
                // Swap first letter to the last letter of the string
                items[i] = Character.toString(item.charAt(item.length() - 1)) 
                          item.substring(1, item.length()-1)
                          Character.toString(item.charAt(0));
            }
        }
        System.out.println(Arrays.toString(items));
    }

}

Output:-

[milk, donut, cookies, cheese]
[imlk, tonud, sookiec, ehcese]