Below program illustrates how to reverse a String using Java:

public class ReverseString {
 
	public static void main(String[] args) {
		String str = "ABCDE";
		String reversed = reverse(str);
		System.out.println(reversed);
	}
	
	public static String reverse(String str) {
		char[] chars = str.toCharArray();
		int len = chars.length;
		for(int i=0, j=len-1; i < len/2; i++, j--) {
			char temp = chars[i];
			chars[i] = chars[j];
			chars[j] = temp;
		}
		return String.valueOf(chars);
	}
 
}