Write a Java program to convert a decimal number to binary.

Here’s a Java program to convert a decimal number to binary:

import java.util.Scanner;

public class DecimalToBinary {
    public static void main(String[] args) {
        int decimalNum;
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a decimal number: ");
        decimalNum = scanner.nextInt();
        String binaryNum = convertToBinary(decimalNum);
        System.out.println("Binary equivalent: " + binaryNum);
    }

    public static String convertToBinary(int decimalNum) {
        String binaryNum = "";
        while (decimalNum > 0) {
            int rem = decimalNum % 2;
            binaryNum = rem + binaryNum;
            decimalNum /= 2;
        }
        return binaryNum;
    }
}

In this program, we first take user input for a decimal number. We then call the `convertToBinary()` method to convert the decimal number to binary.

The `convertToBinary()` method takes an integer parameter `decimalNum` and returns a string representing its binary equivalent. We first initialize an empty string `binaryNum`. We then use a while loop to repeatedly divide the decimal number by 2 and add the remainder to the beginning of the `binaryNum` string. We repeat this process until the decimal number becomes 0. At the end of the method, we return the `binaryNum` string, which is the binary equivalent of the decimal number.

At the end of the program, we print out the binary equivalent of the decimal number.