java 如何在java中创建一个字节数组数组
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How to create an array of byte arrays in java
提问by Alex
I want to create an array of byte[].
When i try:
我想创建一个byte[]. 当我尝试：
byte[] data = new byte[10];
This is an array of byteand not an array of byte[].
Thanks
这是 的数组byte而不是 的数组byte[]。谢谢
回答by Alnitak
In Java, an array where each element is itself an array is effectively just a 2D array, although Java doesn't require that each row have the same number of elements.
在 Java 中，每个元素本身就是一个数组的数组实际上只是一个二维数组，尽管 Java 不要求每一行具有相同数量的元素。
In this particular case where you have a List<byte[]>and you wish to turn that into an array where each element of the array is itself a bytearray you could use:
在这种特殊情况下，您有 aList<byte[]>并且您希望将其转换为一个数组，其中数组的每个元素本身就是一个byte您可以使用的数组：
int rows = myList.size();
byte[][] myArray = new byte[rows][];
int i = 0;
for (byte[] col : myList) {
myArray[i++] = col;
}
or, more succinctly, but less obviously:
或者，更简洁但不那么明显：
byte[][] myArray = myList.toArray(new byte[0][]);
which in use looks like:
使用中的样子：
List<byte[]> myList = new ArrayList<>();
myList.add(new byte[]{1,2,3,4});
myList.add(new byte[]{5,6,7});
myList.add(new byte[]{8,9});
byte[][] myArray = myList.toArray(new byte[0][]);
for (byte[] b : myArray) {
for (byte c : b) {
System.out.println(c);
}
System.out.println();
}
Note that in both cases above the elements of the array are exactlythe same arrays as those stored in the list, not a copy. Therefore if you modify one of the original byte[]elements in the list it'll also change the version accessible via the array.
请注意，在上述两种情况下，数组元素与存储在列表中的数组元素完全相同，而不是副本。因此，如果您修改byte[]列表中的原始元素之一，它也会更改可通过数组访问的版本。
回答by ajb
To address some confusion about "arrays of arrays" and 2D arrays:
为了解决关于“数组数组”和二维数组的一些混淆：
Java doesn't really have 2D arrays. At least, not in the way many people think of them, where they look like a matrix, and you have rows and columns and the same number of elements in each row.
Java 并没有真正的二维数组。至少，不像很多人想象的那样，它们看起来像一个矩阵，你有行和列，每行中有相同数量的元素。
You canuse an "array of arrays" as a 2D array. If you want an array of 5 x 8 integers, you can say
您可以将“数组数组”用作二维数组。如果你想要一个 5 x 8 整数的数组，你可以说
int[][] arr = new int[5][8];
But Java does not enforce the "matrix-ness" or "2D-ness" of an array. What it gives you is an array of 5 references, each of which refers to another array of integers. Each reference starts out referring to an array of 8 integers, but this is not enforced; you could later say
但是 Java 并没有强制执行数组的“矩阵性”或“二维性”。它给你的是一个包含 5 个引用的数组，每个引用都指向另一个整数数组。每个引用开始时引用一个 8 个整数的数组，但这不是强制执行的；你以后可以说
arr[2] = new int[113];
or
或者
arr[2] = null;
and now your array is no longer really a 2D array (as we usually think of it), but Java will not stop you from doing that.
现在你的数组不再是一个真正的二维数组（正如我们通常认为的那样），但 Java 不会阻止你这样做。
So while you may often see something like
所以虽然你可能经常看到类似的东西
byte[][]
used in textbooks to create a 2D array, it's the same syntax as an array of arrays, and Java actually treats it as an array of arrays, not all of which have to be the same size.
教科书上用来创建二维数组的，它和数组数组的语法是一样的，Java实际上是把它当作数组的数组，并不是所有的数组都必须是相同的大小。
If you want to create an array whose elements will eventually bearrays, but that are nullfor now, you can do it like this:
如果你想创建一个数组，它的元素最终将是数组，但null现在是这样，你可以这样做：
byte[][] bytesArray = new byte[10][];
which sets bytesArrayto an array of 10 nullreferences, any one of which could be set later:
它设置bytesArray为一个包含 10 个null引用的数组，其中任何一个都可以稍后设置：
bytesArray[4] = new byte[17];
That would be the way to start, if you want a "ragged array" of arrays that aren't all the same length.
如果您想要一个长度不同的数组的“参差不齐的数组”，那将是开始的方式。
回答by Samuele Panarotto
Try this:
试试这个：
byte[][] arrays = new byte[5][10];
字节[][]数组=新字节[5][10]；
回答by RockOnRockOut
You mean like this?
你的意思是这样？
byte[][] data = new byte[][]{byteArray1, byteArray2, byteArray3};
回答by Lawrence Andrews
In your example, you are creating an array of bytes, if you wanted to create an array of arrays of bytes you would have to create a two dimensional array of bytes:
在您的示例中，您正在创建一个字节数组，如果您想创建一个字节数组数组，则必须创建一个二维字节数组：
byte[][] bytesArray = new byte[10][10];
byte[][] bytesArray = new byte[10][10];
You would then be able to access your array of bytes as follows:
然后，您将能够访问您的字节数组，如下所示：
bytesArray[0]; // returns a byte[]
bytesArray[0]; // returns a byte[]
