float f = ...;
int i = Float.floatToIntBits(f);

See
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Float.html#floatToIntBits(float)

This is code to convert bytes to float.
I need the reverse of this

bytes
   The bytes item of the CONSTANT_Integer_info structure represents
the value of the int constant. The bytes of the value are stored in
big-endian (high byte first) order.

   The bytes item of the CONSTANT_Float_info structure represents the
value of the float constant in IEEE 754 floating-point single format
(§3.3.2). The bytes of the single format representation are stored in
big-endian (high byte first) order.

   The value represented by the CONSTANT_Float_info structure is
determined as follows. The bytes of the value are first converted into
an int constant bits. Then:

       * If bits is 0x7f800000, the float value will be positive
infinity.
       * If bits is 0xff800000, the float value will be negative
infinity.
       * If bits is in the range 0x7f800001 through 0x7fffffff or in
the range 0xff800001 through 0xffffffff, the float value will be NaN.
       * In all other cases, let s, e, and m be three values that
might be computed from bits:

       int s = ((bits >> 31) == 0) ? 1 : -1;
       int e = ((bits >> 23) & 0xff);
       int m = (e == 0) ?
               (bits & 0x7fffff) << 1 :
               (bits & 0x7fffff) | 0x800000;

Then the float value equals the result of the mathematical expression
s·m·2e-150.