The bitwise left shift operator << shifts all the bits to the left by the number of bits specified as its right-hand operand.
It inserts zeros at the lower-order bits.
Shifting 1 bit to left is same as multiplying the number by 2.
9 << 1 is 18, 9 << 2 is 36.
00000000 00000000 00000000 00001001 9 0000000 00000000 00000000 000010010 18 000000 00000000 00000000 0000100100 36
public class Main { public static void main(String[] args) { int i = 9; System.out.println("i = " + (i << 1)); System.out.println("i = " + (i << 2)); } }