从java中的二进制文件读取Double时得到错误的值

发布于 2024-12-14 08:35:20 字数 190 浏览 2 评论 0原文

RandomAccessFile in = new RandomAccessFile("BOT.grd", "r");
in.seek(28);
double xll=in.readDouble();

上面是我用来读取 29 到 36 字节位置的双精度数据的代码。当前的值是 500，但我得到 2.088E-317

原文

RandomAccessFile in = new RandomAccessFile("BOT.grd", "r");
in.seek(28);
double xll=in.readDouble();

The above is the code i am using to read double data which is present from 29 to 36 byte location.The value present is 500 but i am getting 2.088E-317

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寂寞笑我太脆弱 2024-12-21 08:35:20

看起来这个文件存储在与 java 使用的不同的 Endianness 中。在转换为双精度之前，字节可能需要反转，您可以尝试以下代码来读取该值：

long   l = in.readLong();
double d = Double.longBitsToDouble(Long.reverseBytes(l));

这是一个说明问题的示例：

double d = 500.0;

long l1 = Double.doubleToLongBits(d);
long l2 = Long.reverseBytes(l1);

System.out.println(Double.longBitsToDouble(l1));
System.out.println(Double.longBitsToDouble(l2));

输出：

500.0
2.088356E-317

It seems this file is stored in a different Endianness than the one java uses. The bytes probably need to be reversed before converting to double, you could try the following code to read the value:

long   l = in.readLong();
double d = Double.longBitsToDouble(Long.reverseBytes(l));

Here is an example that illustrates the problem:

double d = 500.0;

long l1 = Double.doubleToLongBits(d);
long l2 = Long.reverseBytes(l1);

System.out.println(Double.longBitsToDouble(l1));
System.out.println(Double.longBitsToDouble(l2));

Output: