Suppose I have the following implementations

private static String encryptPassword(String password) {
    String encryptedPassword = "";
    char[] chars = password.toCharArray();
    for (char c : chars) {
        encryptedPassword = encryptedPassword.concat(String.valueOf(  c));
    }
    return encryptedPassword;
}

private static String decryptPassword(String encryptedPassword) {
    String decryptedPassword = "";
    char[] chars = encryptedPassword.toCharArray();
    for (char c : chars) {
        decryptedPassword = decryptedPassword.concat(String.valueOf(--c));
    }
    return decryptedPassword;
}

These methods do very simple stuff that it will increase each character in a string by 1 and this process is considered as encryption. As a contrast, the process of decryption will decrease the value.

I can see that these two methods are pretty much the same, except the unary operators.

How can I generalize these two methods?

Furthermore, I also prefer streaming processing to looping. If you have any ideas regarding this point please posting as well.

CodePudding user response：

Define a enum to specify operaiton type, based on the enum you can apply business logic.

private static enum OperationType {
        ENCRYPTION(1), DECRYPTION(-1);

        int val;

        private OperationType(int val) {
            this.val = val;
        }

    }

    private static String process(final String data, final OperationType operationType) {
        final char[] chars = data.toCharArray();

        final StringBuilder builder = new StringBuilder();
        for (char ch : chars) {

            builder.append(String.valueOf(ch   operationType.val));
        }
        return builder.toString();

    }

To work with streams, you can use string chars method like below.

Stream<Character> charStream = data.chars().mapToObj(i->(char)i);

CodePudding user response：

The difference between the two methods encryptPassword and decryptPassword is the value that you are adding to each char in the String. Therefore I suggest adding a third method that takes two parameters: the first is the String to encrypt (or decrypt) and the second is the value to add to each char. In the below code, I called this third method adjustPassword.

As described in the book Java by Comparison I suggest keeping methods encryptPassword and decryptPassword and have those methods call method adjustPassword with the appropriate value. That way, when you want to encrypt or decrypt a password, you don't need to remember what value to pass for the required operation.

Explanations after the code.

public class Solution {

    private static String encryptPassword(String password) {
        return adjustPassword(password, 1);
    }

    private static String decryptPassword(String encryptedPassword) {
        return adjustPassword(encryptedPassword, -1);
    }

    private static String adjustPassword(String password, int adjustment) {
        StringBuilder sb = new StringBuilder(password.length());
        password.chars()
                .map(c -> c   adjustment)
                .forEach(i -> sb.append((char) i));
        return sb.toString();
    }

    public static void main(String[] args) {
        String password = "George";
        System.out.println("Original: "   password);
        String encrypted = encryptPassword(password);
        System.out.println("Encrypted: "   encrypted);
        System.out.println("Decrypted: "   decryptPassword(encrypted));
    }
}

Running the above code produces the following output:

Original: George
Encrypted: Hfpshf
Decrypted: George

• Since Java 9, class String has method chars() which returns an IntStream since char is essentially an int.
• Class StringBuilder has overloaded append methods. In the forEach method, the type of the method parameter, i.e. i, is int, hence the cast to char, otherwise method adjustPassword would return a String that only contained digits.