Java Program to convert decimal to binary number.
Objective
Write a Java program to manually convert a decimal (base 10) integer into a binary (base 2) string using bitwise operators.
Algorithm / Approach
- Read a decimal integer
xfrom the user. - Run a
forloop counting down from 15 to 0. - In each iteration, perform a right shift operation
r = x >> i. - Use the bitwise AND operator to check the least significant bit:
(r & 1). - If the result is 1, print "1". If it is 0, print "0".
Test.java
import java.util.Scanner;
class Test {
public static void main(String[] a)
{
Scanner s=new Scanner(System.in);
System.out.print("Enter a Num: ");
int x = s.nextInt();
int r;
for(int i = 15; i>=0; i--) {
r = x>>i;
if((r & 1)==1)
System.out.print("1");
else
System.out.print("0");
}
}
}Expected Output
Enter a Num: 10 0000000000001010
Explanation of the Program
- Bitwise operators work directly on the binary representation of the integer in memory.
- By right-shifting the number by
ipositions (x >> i), the bit at positioniis pushed to the furthest right spot (the least significant bit). - The bitwise AND operation
(r & 1)isolates this specific bit, allowing the program to evaluate if it is a 1 or a 0. - The loop runs backwards from 15 to 0 to print the bits in standard left-to-right reading order (starting with the most significant bit of a 16-bit number).
Complexity
Time Complexity
O(1) - The loop runs exactly 16 times regardless of input size.
Space Complexity
O(1)
Common Mistakes
- Printing the bits backwards by running the loop from 0 to 15.
- Forgetting parentheses around
(r & 1) == 1, which can cause evaluation order issues due to Java's operator precedence rules.
