现在我们需要从一个C/C++语言生成的二进制文件中读出一个float数据

想通过java实现怎么实现啊？

说个大概的思路吧：

依据：
[b]
c++和java中的float存储及运算都遵循IEEE754标准。[/b]所以问题就很容易解决。

过程如下：

1，用c++存储float浮点数到二进制文件中，用java文件流操作取二进制文件。

2，获取二进制的字符串，并转化为十六进制数值。

3，然后调用[code="java"]Float.intBitsToFloat(十六进制数值)//比如:0xff7fffff[/code]方法。

[code="c++"]
// 在c++中,用二进制方式写入数值
int main(int argc, char* argv[]){
ofstream outfile("c:\d1.dat");
float f = 12.5f;
outfile.write((char *)&f,sizeof(float));
f = 3332.5f;
outfile.write((char *)&f,sizeof(float));
f = 1442.5224f;
outfile.write((char *)&f,sizeof(float));
outfile.close();
return 0;
}
[/code]

[code="java"]
public static void main(String[] args) throws Exception {
File f = new File("c:/d1.dat");
CppInputStream dis = new CppInputStream(new FileInputStream(f));
System.out.println(dis.readFloat());
System.out.println(dis.readFloat());
System.out.println(dis.readFloat());
}
[/code]

[code="java"]
// 参见java.io.DataInputStream
// C++写入的字节顺序是从低到高（左低到右高），
而java.io.DataInputStream读取的数据是从高到低（左高到右低)
// 所以需要自己改写一下
public class CppInputStream extends FilterInputStream {

public CppInputStream(InputStream in) {
super(in);
}
public final int read(byte b[]) throws IOException {
return in.read(b, 0, b.length);
}

public final int read(byte b[], int off, int len) throws IOException {
return in.read(b, off, len);
}

public final void readFully(byte b[]) throws IOException {
readFully(b, 0, b.length);
}

public final void readFully(byte b[], int off, int len) throws IOException {
if (len < 0)
throw new IndexOutOfBoundsException();
int n = 0;
while (n < len) {
int count = in.read(b, off + n, len - n);
if (count < 0)
throw new EOFException();
n += count;
}
}

public final int skipBytes(int n) throws IOException {
int total = 0;
int cur = 0;
while ((total < n) && ((cur = (int) in.skip(n - total)) > 0)) {
total += cur;
}
return total;
}

public final byte readByte() throws IOException {
int ch = in.read();
if (ch < 0)
throw new EOFException();
return (byte) (ch);
}

public final int readUnsignedByte() throws IOException {
int ch = in.read();
if (ch < 0)
throw new EOFException();
return ch;
}

public final short readShort() throws IOException {
int ch2 = in.read();
int ch1 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (short) ((ch1 << 8) + (ch2 << 0));
}

public final int readUnsignedShort() throws IOException {
int ch2 = in.read();
int ch1 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (ch1 << 8) + (ch2 << 0);
}

public final char readChar() throws IOException {
int ch2 = in.read();
int ch1 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (char) ((ch1 << 8) + (ch2 << 0));
}

public final int readInt() throws IOException {
int ch4 = in.read();
int ch3 = in.read();
int ch2 = in.read();
int ch1 = in.read();
if ((ch1 | ch2 | ch3 | ch4) < 0)
throw new EOFException();
return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
}

private byte readBuffer[] = new byte[8];

public final long readLong() throws IOException {
readFully(readBuffer, 0, 8);
return (((long) readBuffer[7] << 56) + ((long) (readBuffer[6] & 255) << 48)
+ ((long) (readBuffer[5] & 255) << 40) + ((long) (readBuffer[4] & 255) << 32)
+ ((long) (readBuffer[3] & 255) << 24) + ((readBuffer[2] & 255) << 16)
+ ((readBuffer[1] & 255) << 8) + ((readBuffer[0] & 255) << 0));
}

public final float readFloat() throws IOException {
return Float.intBitsToFloat(readInt());
}

public final double readDouble() throws IOException {
return Double.longBitsToDouble(readLong());
}
}
[/code]