The numberOfLeadingZeros() is a static method of the Integer wrapper class that counts the number of zero bits preceding the highest-order (“leftmost”) one-bit in the two’s complement binary representation. In this post, we are going to look at the numberOfLeadingZeros() method in detail.

• Method declaration – public static int numberOfLeadingZeros(int i)
• What does it do? – It will count the number of zero bits preceding the highest-order (“leftmost”) one-bit in the two’s complement binary representation of the int value passed in the argument.
• It will return 32 if the number passed in the argument has no 1-bit set in the 2’s complement of the binary representation, or we can say the number passed in the argument is 0
• What does it return? It will return the count of the number of zero bits preceding the highest-order (“leftmost”) one-bit in the two’s complement binary representation of the int value passed in the argument.
##### Code Example
```public class Codekru {

public static void main(String[] args) {

int i = 21332;

System.out.println("No. of zero bits preceding the leftmost 1-bit in 2's complement representation: "

}
}
```

Output –

``````No. of zero bits preceding the leftmost 1-bit in 2's complement representation: 17
``````

Here, the leading zero bits are counted concerning the 32-bit representation. The 2’s complement binary representation of 21332 is 00000000000000000101001101010100. And so, the number of zeros preceding the leftmost 1 bit is 15.

##### How to calculate 2’s complement of a negative number?
• Positive numbers are just represented by their binary strings but negative numbers are represented by using 2’s complement
• To find the 2’s complement of a number, we first have to know how many bits we are working with. In our case, the number of bits is 32
• Let’s try to find the 2’s complement of the number -30
• For this, we first have to write the binary representation of the number 30
``0000 0000 0000 0000 0000 0000 0001 1110``
• Invert the binary digits
``1111 1111 1111 1111 1111 1111 1110 0001``
• Now, add one to it
``1111 1111 1111 1111 1111 1111 1110 0010``

#### The What If Scenarios

##### Q – What if we pass 0 into the numberOfLeadingZeros() argument?

The function will return 32 as the number of one bit is zero and all of the bits will be counted as leading bits.

```public class Codekru {

public static void main(String[] args) {

System.out.println("No. of zero bits preceding the leftmost 1-bit in 2's complement representation: "

}
}
```

Output –

``No. of zero bits preceding the leftmost 1-bit in 2's complement representation: 32``
##### Q – What if we pass a negative number into the numberOfLeadingZeros() argument?

In this case, numberOfLeadingZeros() would return 0 as the leftmost bit of the 2’s complement representation of a negative number is 1. And so, there will be no 0 bits preceding the 1 bit in case of negative numbers.

```public class Codekru {

public static void main(String[] args) {

int i = -30;

System.out.println("No. of zero bits preceding the leftmost 1-bit in 2's complement representation: "

}
}
```

Output –

``No. of zero bits preceding the leftmost 1-bit in 2's complement representation: 0``

Please visit this link if you want to know more about the Integer wrapper class of java and its other functions or methods.

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