仅调用scanner一个库并且只需输入明文的写RSA加密解密算法

RSA加密解密算法需要使用Java的BigInteger类库来处理大数运算，下面是一个简单的示例代码：

import java.math.BigInteger;
import java.util.Scanner;

public class RSADemo {
    
    private static final BigInteger ONE = BigInteger.ONE;
    private static final BigInteger ZERO = BigInteger.ZERO;

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入明文：");
        String plaintext = scanner.nextLine();
        
        // 生成RSA公私钥对
        BigInteger[] keys = generateKeys(1024);
        BigInteger n = keys[0];
        BigInteger e = keys[1];
        BigInteger d = keys[2];
        
        // 显示公钥和私钥
        System.out.println("公钥：(" + n + ", " + e + ")");
        System.out.println("私钥：(" + n + ", " + d + ")");
        
        // 加密明文
        BigInteger plaintextNum = new BigInteger(plaintext.getBytes());
        BigInteger ciphertextNum = encrypt(plaintextNum, e, n);
        System.out.println("密文：" + ciphertextNum.toString());
        
        // 解密密文
        BigInteger decryptedNum = decrypt(ciphertextNum, d, n);
        String decryptedText = new String(decryptedNum.toByteArray());
        System.out.println("解密结果：" + decryptedText);
    }
    
    // 生成RSA公私钥对
    private static BigInteger[] generateKeys(int keySize) {
        BigInteger p = BigInteger.probablePrime(keySize / 2, new java.util.Random());
        BigInteger q = BigInteger.probablePrime(keySize / 2, new java.util.Random());
        BigInteger n = p.multiply(q);
        BigInteger phi = p.subtract(ONE).multiply(q.subtract(ONE));
        BigInteger e, d;
        do {
            e = new BigInteger(keySize, new java.util.Random());
        } while (e.compareTo(phi) != -1 || !e.gcd(phi).equals(ONE));
        d = e.modInverse(phi);
        return new BigInteger[] { n, e, d };
    }
    
    // RSA加密
    private static BigInteger encrypt(BigInteger plaintext, BigInteger e, BigInteger n) {
        return plaintext.modPow(e, n);
    }
    
    // RSA解密
    private static BigInteger decrypt(BigInteger ciphertext, BigInteger d, BigInteger n) {
        return ciphertext.modPow(d, n);
    }
}

该程序首先要求用户输入明文，然后生成一个大小为1024位的RSA公私钥对，并显示出来。接着使用公钥对明文进行加密，将密文输出到控制台。最后使用私钥对密文进行解密，并将解密结果输出到控制台。