I'm writing a simple Java program to convert from decimal to binary.
public static int toBinary(int n) {
int result = 0;
while (n >= 1) {
int power = 0;
while ((int) Math.pow(2, power) <= n) {
power++;
}
result += (int) Math.pow(10, power - 1);
n = n - (int) Math.pow(2, power - 1);
}
return result;
}
The program works for n up until 1023, but fails after that and I'm not sure where I did wrong. Can someone help?
Your code has a problem of Integer Overflow.
Binary of 1024 is 10,000,000,000 and the max value an int can hold is 2,147,483,647.
Use an int array to store the number:
public static void convertBinary(int num) {
int[] binary = new int[40];
int index = 0;
while (num > 0) {
binary[index++] = num % 2;
num /= 2;
}
for (int i = index - 1; i >= 0; i--){
System.out.print(binary[i]);
}
}
You can also use the in-built method.
System.out.println(Integer.toBinaryString(1024));
You can also use StringBuilder to store the result:
public static void convertBinary(int num){
StringBuilder binary = new StringBuilder();
while (num > 0){
binary.append(num % 2);
num = num / 2;
}
System.out.println(binary.reverse());
}
Do not use String (immutable) in a loop, always use a StringBuilder (mutable).
Intsare already in binary. What you want is the binary representation of a decimal number. So just useInteger.toBinaryString(). If you grow your own, store the result in a String, not an int. Here is one example of how to do it.