Java：如何通过引用传递byte []？ [英] Java: How to pass byte[] by reference?

问题描述

您可以使用关键字ref在.NET中执行此操作。有没有办法在Java中这样做？

You can do it in .NET by using the keyword "ref". Is there any way to do so in Java?

推荐答案

你在做什么方法？如果您只是填充现有数组，那么您不需要传递引用语义 - 无论是在.NET中还是在Java中。在这两种情况下，引用都将按值传递 - 因此调用者可以看到对象的更改。这就像告诉别人你的房子的地址，并要求他们提供一些东西 - 没问题。

What are you doing in your method? If you're merely populating an existing array, then you don't need pass-by-reference semantics - either in .NET or in Java. In both cases, the reference will be passed by value - so changes to the object will be visible by the caller. That's like telling someone the address of your house and asking them to deliver something to it - no problem.

如果你真的想要传递 - 参考语义，即调用者将看到对参数本身所做的任何更改，例如将它设置为null或引用不同的字节数组，然后任一方法需要返回新值，或者您需要将引用传递给某种holder，其中包含对字节数组的引用，并且可以具有稍后从中获取的（可能已更改的）引用。

If you really want pass-by-reference semantics, i.e. the caller will see any changes made to the parameter itself, e.g. setting it to null or a reference to a different byte array, then either method needs to return the new value, or you need to pass a reference to some sort of "holder" which contains a reference to the byte array, and which can have the (possibly changed) reference grabbed from it later.

换句话说，如果您的方法看起来像这样：

In other words, if your method looks likes this:

public void doSomething(byte[] data)
{
    for (int i=0; i < data.length; i++)
    {
        data[i] = (byte) i;
    }
}

然后你很好。如果您的方法如下所示：

then you're fine. If your method looks like this:

public void createArray(byte[] data, int length)
{
    // Eek! Change to parameter won't get seen by caller
    data = new byte[length]; 
    for (int i=0; i < data.length; i++)
    {
        data[i] = (byte) i;
    }
}

然后您需要将其更改为：

then you need to change it to either:

public byte[] createArray(int length)
{
    byte[] data = new byte[length]; 
    for (int i=0; i < data.length; i++)
    {
        data[i] = (byte) i;
    }
    return data;
}

或：

public class Holder<T>
{
    public T value; // Use a property in real code!
}

public void createArray(Holder<byte[]> holder, int length)
{
    holder.value = new byte[length]; 
    for (int i=0; i < length; i++)
    {
        holder.value[i] = (byte) i;
    }
}

有关详细信息，请阅读参数传递C＃和用Java传递参数。 （前者写得比后者好，我很害怕。有一天我会回来做更新。）

For more details, read Parameter passing in C# and Parameter passing in Java. (The former is better written than the latter, I'm afraid. One day I'll get round to doing an update.)

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