Long type Integer calculation

Question

i am now making a source code that calculates long integers, but I don't know why this calculation gives me wrong answer.

long l;
//variable l is where you input long, signed int

l *= 0x6869L;
if(l == 0xeaaeb43e477b8487L)
    System.out.println("Correct!");

I did 0xeaaeb43e477b8487 / 0x6869 = 0xFFFFCBBB6D375815 but when I calculate 0xFFFFCBBB6D375815 * 0x6869 gives 0xEAAEB43E477BA89D.

Why is this thing happens? and what is the real answer of this math question?

Answer 1

This is because when you divide 0xeaaeb43e477b8487L / 0x6869 you lose the remainder, which causes loss of precision.

0xeaaeb43e477b8487L % 0x6869= -9238

if we take it into account we will get

0xEAAEB43E477BA89DL -9238 =  0xeaaeb43e477b8487

this works

if ((l - 9238) == 0xeaaeb43e477b8487L)
    System.out.println("Correct!");