16. What do the following two code fragments do given integers a and b? a-a+b, a

ID: 3736779 • Letter: 1

Question

16. What do the following two code fragments do given integers a and b? a-a+b, a a b, ; Just print the code you wrote with comment 1. Bit reversal. Write a function that takes an integer input, reverse its bits, and returns that integer. For example, if n 8, and the input is 13 (00001101), then its reversal is 176 (10110000). Count the number of 1 bits. Write function that takes an integer input and returns the number of 1's in its binary representation. RGBA color format Some of Java's classes (Bufferedlmage, PixelGrabber) use a special encoding called RGBA to store the color of each pixel. The format consists of four integers, representing the red, green, and blue intensities from 0 (not present) to 255 (fully used), and also the alpha transparency value from 0 (transparent) to 255 (opaque). The four 8-bit integers are compacted into a single 32-bit integer. Write a code fragment to extract the four components from the RGBA integer, and to go the other way. 2. 3.

Explanation / Answer

Hi Student,

16. This program basically swaps the values of two variables.

import java.*;

public class SwapNumbers {

public static void main(String a[]){

int x = 10;

int y = 5;

// Code to swap 'x' (1010) and 'y' (0101)

x = x ^ y; // x now becomes 15 (1111)

y = x ^ y; // y becomes 10 (1010)

x = x ^ y; // x becomes 5 (0101)

System.out.println("After swap: x = "

+ x + ", y = " + y);

}

1. Bit Reversal

class BitReversal

{

// function to reverse bits of a number

public static int reverseBits(int n)

{

int rev = 0;

// traversing bits of 'n'

// from the right

while (n > 0)

{

// bitwise left shift

// 'rev' by 1

rev <<= 1;

// if current bit is '1'

if ((int)(n & 1) == 1)

rev ^= 1;

// bitwise right shift

//'n' by 1

n >>= 1;

}

// required number

return rev;

}

// Driver code

public static void main(String[] args)

{

int n = 8;

System.out.println(reverseBits(n));

}

2. Count the number of 1 bits.

// Java program to Count set

// bits in an integer

import java.io.*;

class countSetBits

{

/* Function to get no of set

bits in binary representation

of positive integer n */

static int countSetBits(int n)

{

int count = 0;

while (n > 0)

{

count += n & 1;

n >>= 1;

}

return count;

}

// driver program

public static void main(String args[])

{

int i = 9;

System.out.println(countSetBits(i));

}

Happy Learning :)