# Java Program to Convert Binary Number to Decimal and vice-versa ## What is a Binary Number?

A binary number is a number represented by a base-2 numeral system, which uses only two symbols: 0 and 1. Each digit, or bit, in a binary number represents a power of 2, with the rightmost bit representing 2^0 and the next bit to the left representing 2^1, and so on.

## Convert a binary number to decimal :

1. Start with the rightmost bit of the binary number and assign it the value 2^0.
2. For each bit moving left, double the previous value and add the value of the current bit.

### Here is an example of how to convert the binary number 1101 to decimal:

1. The rightmost bit is 1, so 2^0 * 1 = 1.
2. The next bit is 1, so 2^1 * 1 = 2.
3. The next bit is 0, so 2^2 * 0 = 0.
4. The leftmost bit is 1, so 2^3 * 1 = 8.
5. Add up all the values (1 + 2 + 0 + 8) to get 11, which is the decimal equivalent of the binary number 1101.

### Example 1:

Run

```public class Main {
public static void main(String[] args) {
String binary = "1101";
int decimal = binaryToDecimal(binary);
System.out.println("Decimal equivalent of binary number " + binary + " is: " + decimal);
}

public static int binaryToDecimal(String binary) {
int decimal = 0;
int binaryLen = binary.length();
for (int i = 0; i < binaryLen; i++) {
int bit = binary.charAt(i) - '0';
int power = binaryLen - i - 1;
decimal += bit * Math.pow(2, power);
}
return decimal;
}
}

```

### Output :

```Decimal equivalent of binary number 1101 is: 13
```

## Convert decimal to binary :

1. Divide the decimal number by 2.
2. Write down the remainder.
3. Repeat step 1 and 2 until the quotient is 0.
4. Read the remainders from bottom to top.

### Here is an example of how to convert the decimal number 13 to binary using the algorithm :

1. Divide 13 by 2: quotient = 6, remainder = 1.
2. Divide 6 by 2: quotient = 3, remainder = 0.
3. Divide 3 by 2: quotient = 1, remainder = 1.
4. Divide 1 by 2: quotient = 0, remainder = 1.
5. Read the remainders from bottom to top: 1101.

### Example 2:

Run

```public class Main {
public static void main(String[] args) {
int decimal = 13;
String binary = decimalToBinary(decimal);
System.out.println("Binary equivalent of decimal number " + decimal + " is: " + binary);
}

public static String decimalToBinary(int decimal) {
String binary = "";
while (decimal > 0) {
binary = (decimal % 2) + binary;
decimal = decimal / 2;
}
return binary;
}
}
```

### Output :

```Binary equivalent of decimal number 13 is: 1101
```

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