How to write a for loop for encoding and decoding in java? the program only encode one letter when I enter a string. College level 1 lesson

I should write a encoding and decoding program in a class and then use it in main. The program needs the position for each letter to increase by 2.

When I run the program, the problem is that when I enter a string (like cookie), only the last letter is encoding. Here is a Screenshot of program running.

What is the problem for my program.

Thanks.

The lesson is very basic tho and the assignment are forbid students import any other java method like base64.Only use the starter code.

The code I will put here as well

public class SimpleCipher {

/*
 * comments here to overview the method
 */
public String encode(String text) {
    String result = "";
    
    
    char[] chars = text.toCharArray();
    int length = chars.length;
        
    
            
    for (char x: chars) {
        
        x+=2;
        
        result = Character.toString(x);
        
    }
    
    
    // ToDo
    // convert text into char array
    // reverse the array using provided method (see below)
    // loop over array adding 2 to each element
    // convert the char array back to a String named result
    // return the resulting String.
    return result;
}

Solution

The main problem is that you are overwriting your result in each iteration. Instead you want to append the character to the result string. You can simply do that with

result = result + Character.toString(x);
result += Character.toString(x); // shorter version
result += x; // java can append characters to strings without explicit conversion

According to the comment that is - even tho it is working - not the desired solution anyways. The task is to create a new character array and fill it.

Do that by creating a new array of the same length as the original, iterating over the indexes of your arrays ( for (int i=0; i<chars.length; i++) ) and for each index write the updated character into the new array. The string class has a constructor that accepts a char array.