# [Java] Conditional Operator XOR

Start review Java recently, this post is written some practice about Conditional Operator - XOR.

If you want to see the Chinese version, please click [here](https://medium.com/@zhao1995.chen/java-%E6%A2%9D%E4%BB%B6%E9%81%8B%E7%AE%97%E5%AD%90-1ad220c3d72e).

### XOR

Full name about XOR is **exclusive or** or **exclusive disjunction**. It is a logical operation that outputs true only when inputs differ (one is true, the other is false). The following is the truth table about XOR.

![註解 2020-05-30 153427.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1590824087233/YD4Hinzia.png)

XOR has reversibility which is different from other conditional operators. Give it an example,

> Set X = 0010, Y = 1001, Z = X XOR Y

> Z = X XOR Y = 0010 XOR 1001 = 1011

> Z XOR X = 1011 XOR 0010 = 1001 = Y

> Z XOR Y = 1011 XOR 1001 = 0010 = X

Using its characteristics, the following are its applications.

* Encryption

```
import java.util.Scanner;

public class XOR {
  public static void main (String[] args) {
    Scanner sc = new Scanner(System.in);
    System.out.println("Please enter a password with a length of 6-12");
		String password = sc.nextLine();

    if(password.length() < 6) {
      System.out.println("Please enter a password longer than 6");
    } else if(password.length() > 12) {
      System.out.println("Please enter a password with a length less than 12");
    } else {
      Key k = new Key();
      System.out.println("Password：" + password);
      System.out.println("Encryption：" + k.encryption(password));
      System.out.println("Decrypt：" + k.decrypt());
    }
	}
}

class Key {
  private String key = "rw14ff18DW8F";
  private String encryptionPassword = "";
  private String decryptPassword = "";

  String encryption(String password) {
    for (int i = 0; i < password.length(); i++) {
      encryptionPassword += (char)(password.charAt(i) ^ key.charAt(i));
    }
    return encryptionPassword;
  }

  String decrypt() {
    for (int i = 0; i < encryptionPassword.length(); i++) {
      decryptPassword += (char)(encryptionPassword.charAt(i) ^ key.charAt(i));
    }
    return decryptPassword;
  }
}
```

Input / Output

```output=
Please enter a password with a length of 6-12
jifjiVNE45
Password：jifjiVNE45
Encryption：W^0}pb
Decrypt：jifjiVNE45
```

* Value Swap

```
import java.util.Scanner;

public class ValueSwap {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int[] swap = new int [2];
    System.out.println("Please enter two integers.");
    for (int i = 0; i < swap.length; i++) {
      swap[i] = sc.nextInt();
    }
    ValueSwap.swap(swap);
  }

  public static void swap(int[] swap) {
    swap[0] = swap[0] ^ swap[1];
    swap[1] = swap[0] ^ swap[1];
    swap[0] = swap[0] ^ swap[1];
  }
}
```
Input / Output
```output=
Please enter two integer.
15 89
89 15
```


The above are some exercises on XOR. If you have any suggestions, please leave a message below. Thank you.