重新用java把全部代码写出来

好的，以下是完整的 Java 代码：

import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.util.Random;

public class RSA {
    private BigInteger p;
    private BigInteger q;
    private BigInteger n;
    private BigInteger phi;
    private BigInteger e;
    private BigInteger d;

    public RSA(BigInteger p, BigInteger q) {
        this.p = p;
        this.q = q;
        this.n = p.multiply(q);
        this.phi = p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));
        this.e = generateE(phi);
        this.d = e.modInverse(phi);
    }

    public BigInteger encrypt(String message) {
        byte[] bytes = message.getBytes(StandardCharsets.UTF_8);
        BigInteger m = new BigInteger(bytes);
        return m.modPow(e, n);
    }

    public String decrypt(BigInteger cipher) {
        BigInteger m = cipher.modPow(d, n);
        byte[] bytes = m.toByteArray();
        return new String(bytes, StandardCharsets.UTF_8);
    }

    private BigInteger generateE(BigInteger phi) {
        BigInteger e = BigInteger.probablePrime(phi.bitLength(), new Random());
        while (!phi.gcd(e).equals(BigInteger.ONE)) {
            e = BigInteger.probablePrime(phi.bitLength(), new Random());
        }
        return e;
    }

    public static void main(String[] args) {
        BigInteger p = BigInteger.valueOf(17);
        BigInteger q = BigInteger.valueOf(19);
        RSA rsa = new RSA(p, q);
        String message = "Hello, world!";
        System.out.println("Original message: " + message);
        BigInteger cipher = rsa.encrypt(message);
        System.out.println("Encrypted message: " + cipher);
        String decryptedMessage = rsa.decrypt(cipher);
        System.out.println("Decrypted message: " + decryptedMessage);
    }
}

这个程序可以生成一个 RSA 密钥对，加密和解密字符串消息。在 `main` 方法中，我们使用了一个简单的示例消息 "Hello, world!" 进行加密和解密，您可以根据需要修改这个消息。