decimal to binary using stacks

import java.util.*;
import java.lang.Math;;

interface Stack<E> {
    E top();

    E pop();

    void push(E element);

    boolean isEmpty();
}

class ArrayStack<E> implements Stack<E> {
    public E arr[];
    private int t = -1;

    public int size() {
        return t + 1;
    }

    public ArrayStack(int capacity) {
        arr = (E[]) new Object[capacity];
    }

    public boolean isEmpty() {
        if (size() == 0) {
            return true;

        }
        return false;
    }

    public void push(E element) throws IllegalStateException {
        if (size() == arr.length) {
            throw new IllegalStateException("Stack is full");
        }
        // size++;
        arr[++t] = element;
    }

    public E pop() {
        if (isEmpty()) {
            return null;
        }
        E e = top();
        --t;
        return e;
    }

    public E top() {
        if (isEmpty()) {
            return null;
        }
        return arr[size() - 1];
    }
}
class dec_to_bin{
    ArrayStack<Long> a1=new ArrayStack<Long>(32);

    public void pushing(double num){
        while(num>=0){
        long x=(long)num % 2;
        a1.push(x);
        long y=(long)num/2;
        num=y;
        }
    }

    public void process(double num){
        double fracpart=num % 1;                //This 2 lines will separate the integer part and fractional part of the number given
        long intpart=(long)num-(long)fracpart;
        if(fracpart==0){                            //Checking if the given number is a floating point

            pushing(num);                   //This method will push the 1/0 onto the stack
            int len=a1.arr.length;
            for(int i=0;i<len;i++){         //This for loop will print the stack i.e. the binary number will get printed
                long e=a1.pop();
                System.out.print(e);
            }
            System.out.println();
        }
        else{
            pushing(intpart);       //Since the number contains fractional part so I have implemented stack only for the integer part
            int a[]=new int[23];
            int i=0;
            while(i<23){
                fracpart=Math.round(fracpart*10000)/10000.0;
                double y=fracpart*2;
                int x=(int)y/10000;
                a[i++]=x;
                fracpart=y-x;
                if(fracpart==0)
                break;
            }
            int len=a1.arr.length;
            for(int j=0;j<len;j++){         //Loop= to print the integer part of binary number
                long e=a1.pop();
                System.out.print(e);
            }
            System.out.print(".");
            for(int k=0;k<a.length;k++){        //Loop= to print the fractional part of binary number
                System.out.print(a[k]);
            }
            System.out.println();
        }
    }
}
public class Main {
    public static void main(String args[]){
        Scanner sc=new Scanner(System.in);
        dec_to_bin d1 =new dec_to_bin();
        System.out.println("Enter decimal number");
        double nu=sc.nextDouble();
        d1.process(nu);
    }
}