# Java - left shift operator

The Bitwise left shift operator (<<) takes the two numbers and left shift the bits of first operand by number of place specified by second operand. For example: for left shifting the bits of x by y places, the expression (x<<y) can be used. It is equivalent to multiplying x by 2y.

The example below describes how left shift operator works:

```1000 << 2 returns 4000

(In Binary)
1000         ->    1111101000
<< 2                     |  left shift the bits
-----                    V  by 2 places
4000         <-  111110100000
(In Binary)
```

The code of using left shift operator (<<) is given below:

```public class MyClass {
public static void main(String[] args) {
int x = 1000;
int z;

//left shift operation
z = x << 2;

//Displaying the result
System.out.println("z = "+ z);
}
}
```

The output of the above code will be:

```z = 4000
```

### Example: Count number of 1 Bits in a positive integer

Consider an integer 1000. In the bit-wise format, it can be written as 1111101000. However, all bits are not written here. A complete representation will be 32 bit representation as given below:

```00000000000000000000001111101000
```

Bitwise AND operation with 1 at any bit results into 1 if the bit is 1 or 0 if the bit is 0. Performing such operation at every bit, and counting the number of 1 gives the count of 1 bits in the given positive integer. To achieve this bitwise left shift operator can be used as shown in the example below:

```public class MyClass {
static int CountOneBits(int n) {
int count = 0;

//performing bitwise AND operation
//at every bit of the number
for(int i = 0; i < 32; ++i) {
count++;
}
return count;
}

public static void main(String[] args) {
System.out.println("CountOneBits(1000) = "+
CountOneBits(1000));
System.out.println("CountOneBits(1023) = "+
CountOneBits(1023));
}
}
```

The above code will give the following output:

```CountOneBits(1000) = 6
CountOneBits(1023) = 10
```

❮ Java - Operators

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