Question

嘿，我正在创建关于密码学的新项目这是我的代码：

private void encCaesar() {

    char[] chars = plaintext.toCharArray();
    for (int z = 0; z < plaintext.length(); z++) {
        char c = chars[z];
        if (c >= 32 && c <= 125) {
            int x = c - 32;
            x = (x + keyCaesar) % 96;
            if (x < 0)
                x += 96;
            chars[z] = (char) (x + 32);
        }
    }
    tempCipher = new String(chars);
    Log.d("Caesar", tempCipher);  

}

private void encRF() {

    int skip;
    int i, d, j;

    for (d = 0; d < keyRF - 1; d++) {
        skip = 2 * (keyRF - d - 1);
        j = 0;
        for (i = d; i < tempCipher.length();) {

            ciphertext += tempCipher.charAt(i);
            if ((d == 0) || (j % 2 == 0))
                i += skip;
            else
                i += 2 * (keyRF - 1) - skip;
            j++;
        }
    }

    for (i = d; i < tempCipher.length(); i += 2 * (keyRF - 1)) {
        ciphertext += tempCipher.charAt(i);
    }
    Log.d("RF", ciphertext);  
    etCipher.setText(ciphertext);
}

btnEnc.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {
            // TODO Auto-generated method stub
            try {

                keyRF = 2;
                String tempkey = key1.getText().toString();
                plaintext = etPlain.getText().toString();
                if (plaintext.trim().equals("")) {
                    {
                        AlertDialog alertDialog = new AlertDialog.Builder(
                                SentSMSActivity.this).create();
                        alertDialog.setTitle("Alert Dialog");
                        alertDialog
                                .setMessage("Plain text masih kosong . . .");
                        alertDialog.setButton("OK",
                                new DialogInterface.OnClickListener() {
                                    public void onClick(
                                            DialogInterface dialog,
                                            int which) {
                                    }
                                });

                        alertDialog.show();
                    }

                }
                if (tempkey.trim().equals("")) {
                    Toast.makeText(
                            getBaseContext(),
                            "Key 1 masih kosong, maka akan digunakan digunakan key default yaitu 2",
                            Toast.LENGTH_SHORT).show();
                    key1.setText("2");
                } else if (Integer.parseInt(tempkey) > plaintext.trim()
                        .length() - 1) {
                    Toast.makeText(
                            getBaseContext(),
                            "Key 1 nilainya melebihi plaintext, maka akan digunakan digunakan key default yaitu 2",
                            Toast.LENGTH_SHORT).show();
                    key1.setText("2");
                } else {
                    keyRF = Integer.parseInt(key1.getText().toString());
                }

                keyCaesar = 3;
                if (key2.getText().toString().trim().equals("")) {
                    Toast.makeText(
                            getBaseContext(),
                            "Key 2 masih kosong, maka akan digunakan digunakan key default yaitu 3",
                            Toast.LENGTH_SHORT).show();
                    key2.setText("3");
                } else {
                    keyCaesar = Integer.parseInt(key2.getText().toString());
                }

            } finally {

                tempCipher = "";
                encCaesar();
                encRF();

            }
        }
    });

点击加密后，首先加密凯撒然后加密。我做了相反的RF然后Caesar工作正常但是当凯撒出现射频问题时所以问题是密文应该是“XYZ”而是出现“nullXYZ”

Answer 1

null当转换为String时，字符串变为'null'。尝试使用

初始化String变量

String ciphertext = "";

Java null出现在文本前面

1 个答案: