如何从两个 n 位二进制数创建一个 2n 位二进制数？

Question

Lets suppose i have n=4 so two 4-bit binary numbers. B1 = b1010 and B2 = b0110 .
I want to create an 8-bit number that looks like this b10100110 (B1B2).
How can i do such a thing in Java?

Answer 1

Multiply one by 16 , which is the same as adding four zeroes to the end. Then add them. In general, multiplying by 2^n adds n zeroes .

Answer 2

You can of course multiply and add them as suggested. I prefer using bit manipulation operators.

       int b1 = 0b1010;
       int b2 = 0b0110;

       // shift b1 left 4 bits and then OR it with b2.
       int result = (b1<<4)|b2;

       System.out.println(Integer.toBinaryString(result));

As a side note, for every bit you shift left, you are multiplying by a power of 2. So shifting left by 4 bits is multiplying by 16. For right shifting, you are dividing by powers of 2.