Java：有整数，需要 0x00 格式的字节

Java: have integer, need it in byte in 0x00 format

提问by CQM

I have an integer used to seed my for loop:

我有一个整数用于为我的 for 循环做种子：

for(int i = 0; i < value; i++)

Within my for loop I am seeding a byte array with byte content values that increment +1. For instance new byte[]{0x00};But the 0x00needs to be 0x01on the next iteration, how can I convert my value of integer iinto a value of byte in the 0x00 format?

在我的 for 循环中，我正在播种一个字节数组，其中的字节内容值递增 +1。例如new byte[]{0x00};但是0x00需要0x01在下一次迭代中，如何将整数值i转换为 0x00 格式的字节值？

I tried things like Byte.valueOf(Integer.toHexString(i))but this just gives me a value that looks like 0instead of 0x00.

我尝试过类似的事情，Byte.valueOf(Integer.toHexString(i))但这只是给了我一个看起来像0而不是0x00.

回答by ruakh

new byte[]{0x00}

is actually equivalent to

实际上相当于

new byte[]{0}

The 0x00 notation is just an alternative way to write integer constants, and if the integer constant is in the range -128 to 127, then it can be used as a byte.

0x00 表示法只是写整数常量的另一种方式，如果整数常量在 -128 到 127 的范围内，则可以将其用作字节。

If you have an existing integer variable that you want to use, and its value is in the range -128 to 127, then you just have to cast it:

如果您有一个要使用的现有整数变量，并且它的值在 -128 到 127 的范围内，那么您只需将其强制转换：

int i = 1;
new byte[]{(byte)i};

回答by Stephen C

I think the real problem is that you are confused about number representations and text renderings of numbers. Here are some key facts that you need to understand:

我认为真正的问题是您对数字的数字表示和文本渲染感到困惑。以下是您需要了解的一些关键事实：

• The bytetype is the set of integral values from -128 to +127.

• All integral types use the same representation (2's complement). The difference between the different types is their ranges.

• When you "see" a number, what you are seeing is a rendering of the number into a sequence of characters. There are MANY possible renderings; e.g. the number represented in memory as 00101010(42) can be rendered as "42"or "+42"or "0x2a"or ... "forty two".

• The default format for rendering a byte, short, intand longis the same; i.e. an optional minus sign followed by 1 or more decimal digits (with no zero padding). If you want to see your numbers formatted differently, then you need to do the formatting explicitly; e.g. using String.format(...).

• 的byte类型是一组的整数值的从-128到+127。

• 所有整数类型都使用相同的表示（2 的补码）。不同类型之间的区别在于它们的范围。

• 当您“看到”一个数字时，您所看到的是将数字呈现为一系列字符。有许多可能的渲染；例如，在内存中表示为00101010(42) 的数字可以呈现为"42"or"+42"或"0x2a"or ... "forty two"。

• 为渲染的默认格式byte，short，int并且long是相同的; 即一个可选的减号，后跟 1 个或多个十进制数字（没有零填充）。如果你想看到你的数字格式不同，那么你需要明确地进行格式化；例如使用String.format(...).

So to pull this together, if you want the bytes to look like 0x00and 0x01when you output or display them, you need to format them appropriately as you output / display them. In your example code, I doubt that there is anything wrong with the numbers themselves, or with the loop you are using to populate the array.

因此，要将这些组合在一起，如果您希望字节看起来像0x00并且0x01在输出或显示它们时，您需要在输出/显示它们时适当地格式化它们。在您的示例代码中，我怀疑数字本身或用于填充数组的循环有什么问题。

回答by Grodriguez

You are confusing the string representationof the value with the value itself. A value can be represented as binary, decimal, or hex, but it is still the same value.

您将值的字符串表示与值本身混淆了。一个值可以表示为二进制、十进制或十六进制，但它仍然是相同的值。

If you want to use your integer to initialise a byte array, you just need to cast your integer value to a byte value as follows:

如果要使用整数初始化字节数组，只需将整数值转换为字节值，如下所示：

arr[i] = (byte) i;

回答by Ingo

You want

你要

new byte[]{(byte)i}

How you print this array is another matter. Look up printf in the API reference.

如何打印这个数组是另一回事。在 API 参考中查找 printf。

回答by Peter Black

I would just like to note that 0 is NOT the same thing as 0x00. If i were to use:

我只想指出 0 与 0x00 不同。如果我要使用：

ColorChooserOutputText.append(Integer.toHexString(list[i].getRed()));                                           
ColorChooserOutputText.append(Integer.toHexString(list[i].getGreen()));                                      
ColorChooserOutputText.append(Integer.toHexString(list[i].getBlue()));

and wanted to return the color, Purple it would return: ff0cc Which would be fine if I were just using Java. But if you are going between Java and something that had format specific needs ff0cc would not produce purple.. ff00cc is actually purple.

并且想要返回颜色，Purple 它会返回：ff0cc 如果我只是使用 Java，这会很好。但是，如果您在 Java 和具有特定格式需求的东西之间切换，ff0cc 不会产生紫色.. ff00cc 实际上是紫色的。

    //Declare some variables.
    Color HexColor = JButton1.getBackground();

    String MyRValue = null;
    String MyGValue = null;
    String MyBValue = null;

    //Get Hex Value
    MyRValue = Integer.toHexString(HexColor.getRed());
    MyGValue = Integer.toHexString(HexColor.getGreen());
    MyBValue = Integer.toHexString(HexColor.getBlue());

    //Make sure to keep both 0's                    
    MyRValue = ("00"+MyRValue).substring(MyRValue.length());
    MyGValue = ("00"+MyGValue).substring(MyGValue.length());
    MyBValue = ("00"+MyBValue).substring(MyBValue.length());

    //Format your HexColor to #00ff00, #000000, #ff00ee
    JTextArea1.append("#");
    JTextArea1.append(MyRValue+MyGValue+MyBValue);
    JTextArea1.append(", ");

回答by paulsm4

String.Format ("%02x") is your friend :)

String.Format ("%02x") 是你的朋友 :)

http://download.oracle.com/javase/1.5.0/docs/api/java/util/Formatter.html

http://download.oracle.com/javase/1.5.0/docs/api/java/util/Formatter.html

http://www.xinotes.org/notes/note/1195/

http://www.xinotes.org/notes/note/1195/