Is there cast in Java similar to in C++

Question

I get in my function message array of bytes and type of object, I need to restore object from bytes. Is there in Java any cast like in C++ ?

Answer 1

If you really want to take a block of memory, and reinterpret it as a java object, you can achieve that through sun.misc.Unsafe.

You'd need to iterate the class/type of the object, find all the valid fields you'd need to set, read their specific types out of the off-heap memory buffer, and set them via reflection.

It's not something I'd recommend, making use of other serialization mechanics would be a much better alternative.

Edit: Something like this perhaps:

class Test {
    int x;
    int y;
}

public static void main(String[] args) throws Exception {
    final Unsafe unsafe = Unsafe.getUnsafe();

    final int count = 2;
    final long address = unsafe.allocateMemory(Integer.BYTES * count);

    for (int i = 0; i < count; ++i) {
        unsafe.putInt(address + i * Integer.BYTES, ThreadLocalRandom.current().nextInt(0, 10));
    }

    final Class klass = Test.class;
    final Test test = klass.newInstance();

    int i = 0;
    for (final Field f : klass.getDeclaredFields()) {
        f.setAccessible(true);
        f.putInt(test, unsafe.getInt(address + i * Integer.BYTES));

        ++i;
    }
}

Of course you easily reinterpret these primitives into anything. I don't even have to Unsafe#putInt, but obviously I need ints according to Test