添加“\0”后，是否可以将数据添加到字符串中（空值）？ [英] Is it possible to add data to a string after adding "\0" (null)?

问题描述

我有一个我正在创建的字符串，我需要在字符串中添加多个\0（空）字符。在每个空字符之间，是其他文本数据（Just ASCII字母数字字符）。

I have a string that I am creating, and I need to add multiple "\0" (null) characters to the string. Between each null character, is other text data (Just ASCII alphanumeric characters).

我的问题是在J2SE中添加第一个null（\0）时，java然后似乎确定它是一个字符串终止符（类似于C ++），并忽略所有其他附加数据。不会引发错误，只会忽略尾随数据。我需要在字符串中的null之后强制添加其他尾随数据。我必须为我支持的遗留数据库执行此操作。

My problem is that in J2SE when you add the first null (\0), java then seems to determine that it's a string terminator, (similar to C++), and ignores all other data being appended. No error is raised, the trailing data is just ignored. I need to force the additional trailing data after a null in the string. I have to do this for a legacy database that I am supporting.

我试图对字符串进行编码/解码，希望像％00这样的内容会欺骗字符串行为，但是当我重新编码字符串时，Java再次看到空字符，并在第一个空字符后删除所有数据。

I have tried to encode/decode the string in hoping that something like %00 would fool the interpretation of the string behaviour, but when I re-encode the string, Java sees the null character again, and removes all data after the first null.

更新：这是相关的代码段。是的，我正在尝试使用 Strings 。我打算尝试使用字符，但我仍然需要将它作为字符串保存到数据库中，所以我怀疑我最终会遇到同样的问题。

Update: Here is the relevant code snippet. Yes, I am trying to use Strings. I intend to try chars, but I still have to save it into the database as a string, so I suspect that I will end up with the same problem.

一些背景知识。我通过HTTP帖子接收数据，其中包含\ n。我需要删除换行符并用\0替换它们。 debug 方法只是一个简单的方法 System.out.println 。

Some background. I am receiving data via HTTP post that has "\n". I need to remove the newlines and replace them with "\0". The "debug" method is just a simple method that does System.out.println.

                String[] arrLines = sValue.split("\n");
                for(int k=0;k<arrLines.length;k++) {
                    if (0<k) {
                        sNewValue += "\0";
                    }
                    sNewValue+= arrLines[k];
                    debug("New value =" + sNewValue);
                }

sNewValue，一个字符串，提交到数据库，需要像以下一样完成一个字符串。当我在控制台中每次迭代后显示 sNewValue 的当前值时，我观察到的是这样的：

sNewValue, a String, is committed to the database and needs to be done as a String. What I am observing when i display the current value of sNewValue after each iteration in the console is something like this:

输入为value1 \\\
Value2 \\\
Value3
控制台中的输出从此代码中提供给我

input is value1\nValue2\nValue3 Output in the console is giving me from this code

value1
value1
value1

我期待

value1
value1 value2
value1 value2 value3 

分别在value1，value2和value3之间使用不可打印的null。请注意，实际保存回数据库的值也只是value1。因此，它不仅仅是一个控制台显示问题。 \0之后的数据被忽略。

with non-printable null between value1, value2 and value3 respectively. Note that the value actually getting saved back into the database is also just "value1". So, it's not just a console display problem. The data after \0 is getting ignored.

推荐答案

我强烈怀疑这无关紧要与字符串本身的文本 - 我怀疑它是如何显示。例如，试试这个：

I strongly suspect this is nothing to do with the text in the string itself - I suspect it's just how it's being displayed. For example, try this:

public class Test {
    public static void main(String[] args) {
        String first = "first";
        String second = "second";
        String third = "third";
        String text = first + "\0" + second + "\0" + third;
        System.out.println(text.length()); // Prints 18
    }
}

这打印18，显示所有人物存在。但是，如果您尝试在UI标签中显示 text ，我只会看到第一个并不会感到惊讶。 （在相当弱的调试器中也是如此。）

This prints 18, showing that all the characters are present. However, if you try to display text in a UI label, I wouldn't be surprised to see only first. (The same may be true in fairly weak debuggers.)

同样你应该可以使用：

 char c = text.charAt(7);

现在 c 应为'e'这是第二个的第二个字母。

And now c should be 'e' which is the second letter of "second".

基本上，我希望Java的核心不是关心它包含U + 0000的事实。就Java而言，它只是另一个角色。只有在与本机代码（例如显示器）的边界处，它才可能导致问题。

Basically, I'd expect the core of Java not to care at all about the fact that it contains U+0000. It's just another character as far as Java is concerned. It's only at boundaries with native code (e.g. display) that it's likely to cause a problem.

如果这没有帮助，请完整地解释 你所观察到的 - 它是什么让你认为其余的数据没有附加。

If this doesn't help, please explain exactly what you've observed - what it is that makes you think the rest of the data isn't being appended.

编辑：另一种诊断方法是打印出来字符串中每个字符的Unicode值：

Another diagnostic approach is to print out the Unicode value of each character in the string:

for (int i = 0; i < text.length(); i++) {
    System.out.println((int) text.charAt(i));
}

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