Write a Java program to convert a decimal no to binary?

Answer 1

Here's a simple Java method to perform the conversion from decimal to a binary string representation:
public String toBinaryString(int n) {
StringBuilder sb = new StringBuilder();
while(n != 0) {
sb.insert(0, n % 2 != 0 ? '1' : '0');
n /= 2;
}
return sb.toString();
}

The java.lang.Integer class provides a conversion helper method between decimal (integer) and binary numbers in string form called toBinaryString().

String binaryValue = Integer.toBinaryString(43) // 43-> "101011"

Answer 2

You can't. While Java supports hexadecimal and octal literals, there is no native support for binary. You need to use/write a method to do the conversions for you.