Unsafe申请堆外内存

    @Test
    public void testUnsafeAllocateMemory() throws IllegalAccessException {
        Field unsafeField = Unsafe.class.getDeclaredFields()[0];
        unsafeField.setAccessible(true);
        Unsafe unsafe = (Unsafe) unsafeField.get(null);

        //申请4字节大小的内存空间，并得到对应位置的地址
        long address = unsafe.allocateMemory(4);
        //在对应的地址上设定int的值
        unsafe.putInt(address, 6666666);
        //获取对应地址上的Int型数值
        System.out.println(unsafe.getInt(address));
        //释放申请到的内容
        unsafe.freeMemory(address);

        //由于内存已经释放，这时数据就没了
        System.out.println(unsafe.getInt(address));


    }