Reverse a string in Java

To reverse a string in Java, you can use the following approaches:

  1. Using a for loop:
public class Main {
  public static void main(String[] args) {
    String str = "Hello";
    StringBuilder sb = new StringBuilder();

    for (int i = str.length() - 1; i >= 0; i--) {
      sb.append(str.charAt(i));
    }

    String reversed = sb.toString();
    System.out.println(reversed);  // Output: "olleH"
  }
}
  1. Using the reverse method of the StringBuilder class:
public class Main {
  public static void main(String[] args) {
    String str = "Hello";
    String reversed = new StringBuilder(str).reverse().toString();
    System.out.println(reversed);  // Output: "olleH"
  }
}
  1. Using the String.join method (Java 8+):
public class Main {
  public static void main(String[] args) {
    String str = "Hello";
    String reversed = String.join("", str.chars().mapToObj(c -> String.valueOf((char)c)).collect(Collectors.toList()).stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList()));
    System.out.println(reversed);  // Output: "olleH"
  }
}

I hope this helps! Let me know if you have any other questions.