一个 output 如何在 codeRunner 中返回 java 中的单词之间没有空格？

Question

Write algorithm that outputs a string with no spaces using caesar-cipher algorithm into coderunner. Lecturer mentioned string+= "" adds no spacing because the ASCI character 32 adds a space to the string. I do not know how to implement this into code because confused with the string.length concept and how to use str += in this code. input encrypt2("are we human", 2) output: ctgygjwocp?

public class Tester {
        
        public String encrypt(String plainText, int offset) {
                String cipher = new String("");
                char[] arr = plainText.toCharArray();       
                        for (int i = 0; i<arr.length; i++){     
                            int numericalVal = (int) arr[i];   
                            if(Character.isUpperCase(arr[i])) {    
                                cipher += (char) (((numericalVal+offset-65) %26) +65);   
                            } else if (numericalVal == 32){
                                cipher+=arr[i];
                            } else {cipher += (char) (((numericalVal+offset-97) %26) +97);  
                            } 
                        }
                        return cipher;
                }
              
        public static void main(String[] args) {
                    String cipher +="";
                     system.out.println("are we human") }
                          
                        }

Answer 1

public static String encrypt(String plainText, int offset) {
    String cipher = "";

    char[] arr = plainText.toCharArray();
    for (char c : arr) {
        if (Character.isUpperCase(c)) {
            cipher += (char) (((c + offset - 65) % 26) + 65);
        } else if (c == 32){
            cipher+="";   //<---- append nothing if space
        } else {
            cipher += (char) (((c + offset - 97) % 26) + 97);
        }
    }
    return cipher;
}

You can also do plainText = plainText.replaceAll(" ", ""); and you won't have to check for character 32.

public static String encrypt(String plainText, int offset) {
    String cipher = "";
    
    plainText = plainText.replaceAll(" ", "");

    char[] arr = plainText.toCharArray();
    for (char c : arr) {
        if (Character.isUpperCase(c)) {
            cipher += (char) (((c + offset - 65) % 26) + 65);
        } else {
            cipher += (char) (((c + offset - 97) % 26) + 97);
        }
    }
    return cipher;
}