DES加密解密算法java实现代码密钥自己输入

下面是一个简单的DES加密解密算法的Java实现代码，密钥由用户输入：

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import java.util.Base64;
import java.util.Scanner;

public class DesDemo {

    private static final String ALGORITHM = "DES";

    public static void main(String[] args) throws Exception {
        Scanner scanner = new Scanner(System.in);

        // 获取密钥
        System.out.print("请输入密钥：");
        String keyString = scanner.nextLine();
        byte[] keyBytes = keyString.getBytes();

        // 生成密钥
        DESKeySpec keySpec = new DESKeySpec(keyBytes);
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
        SecretKey key = keyFactory.generateSecret(keySpec);

        // 加密
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);
        System.out.print("请输入要加密的字符串：");
        String input = scanner.nextLine();
        byte[] inputBytes = input.getBytes();
        byte[] encryptedBytes = cipher.doFinal(inputBytes);
        String encryptedString = Base64.getEncoder().encodeToString(encryptedBytes);
        System.out.println("加密后的字符串：" + encryptedString);

        // 解密
        cipher.init(Cipher.DECRYPT_MODE, key);
        byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(encryptedString));
        String decryptedString = new String(decryptedBytes);
        System.out.println("解密后的字符串：" + decryptedString);
    }
}

运行该程序，会提示用户输入密钥和要加密的字符串，然后输出加密后的字符串和解密后的字符串。请注意，此处使用了Java的Base64编码和解码工具类，需要在Java 8及以上版本中使用。