Java lang.Long.highestOneBit() method in Java with Examples

java.lang.Long.highestOneBit() is a built-in method in Java which first convert the number to Binary, then it looks for the first set bit from the left, then it reset rest of the bits and then returns the value. In simple language, if the binary expression of a number contains a minimum of a single set bit, it returns 2^(last set bit position from right-1). If the binary expression does not contain any set bit, it returns 0.

Syntax:

public static long highestOneBit(long num)
Parameters:
num - the number passed 
Returns:
long value by only considering highest 1 bit in the argument.

Examples:

Input : 9 
Output : 8
Explanation: Binary Representation = 1001
It considers highest bit(at 4th from right) and now
reset rest of the bits i.e. 1000
so result = 1000 i.e. 8 or in simple terms, the last set 
bit position from right is at position 4, hence 2^3=8

Input : 45
Output : 32

The program below illustrates the java.lang.Long.highestOneBit() function:

Program 1:

// Java program that demonstrates the use of
// Long.highestOneBit() function

// include lang package
import java.lang.*;

public class GFG {

    public static void main(String[] args)
    {

        long l = 9;

        // returns a long value with at most a
        // single one-bit, in the position
        // of the highest-order ("rightmost")
        // one-bit in the specified long value.
        System.out.println("highest one bit = " + Long.highestOneBit(l));

        l = 45;
        System.out.println("highest one bit = " + Long.highestOneBit(l));
    }
}

Output:

highest one bit = 8
highest one bit = 32

Note: The negative number’s highest bit will always be the same in every case, hence irrespective of the number, the output will be same for every negative number.

Program 2: The program below demonstrates the use of function when a negative number is passed.

// java program that demonstrates the use of
// Long.highestOneBit() function
// negative number

// include lang package
import java.lang.*;

public class GFG {

    public static void main(String[] args)
    {

        long l = -15;

        // prints the binary of a negative expression
        System.out.println("Binary = " + Long.toBinaryString(l));

        // returns a long value with at
        // most a single one-bit, in the position
        // of the highest-order ("rightmost")
        // one-bit in the specified int value.
        System.out.println("Highest one bit = " + Long.highestOneBit(l));
    }
}

Output:

Binary = 1111111111111111111111111111111111111111111111111111111111110001
Highest one bit = -9223372036854775808

It returns an error message when a decimal a string value is passed as an argument.
Program 3: When a decimal value is passed in argument.

// java program that demonstrates the
// Long.highestOneBit() function
// decimal value in argument

// include lang package
import java.lang.*;

public class GFG {

    public static void main(String[] args)
    {

        System.out.println("highest one bit = " + Long.highestOneBit(12.34));
    }
}

Output:

prog.java:13: error: incompatible types: possible lossy conversion from double to long
        System.out.println("highest one bit = " + Long.highestOneBit(12.34));

Program 3: When a string value is passed in argument.

// java program that demonstrates the
// Long.highestOneBit() function
// string value in argument

// include lang package
import java.lang.*;

public class GFG {

    public static void main(String[] args)
    {

        System.out.println("highest one bit = " + Long.highestOneBit("12"));
    }
}

Output:

prog.java:13: error: incompatible types: String cannot be converted to long
        System.out.println("highest one bit = " + Long.highestOneBit("12"));