how to get binary value in java

1public static String makeBinaryString(int n) {
2	StringBuilder sb = new StringBuilder();
3	while (n > 0) {
4    sb.append(n % 2);
5		n /= 2;
6	}
7  	sb.reverse();  	
8  	return sb.toString();
9}

1import java.util.*;
2
3class Bin {
4
5    //fields
6    private Double number;
7
8    //constructors
9    public Bin(){
10        number = 0.0;
11    }
12
13    public Bin(Double num){
14        number = num;
15    }
16
17    //methods
18    public ArrayList<String> reverseArrayList(ArrayList<String> alist) {
19        
20        ArrayList<String> array = new ArrayList<String>();
21
22        int x = 0;
23        int i = alist.size() - 1;
24
25        while(x < alist.size()){
26            array.add(alist.get(i));
27            i -= 1;
28            x += 1;
29        }
30
31        return array;
32    }
33
34	//getter methods
35    public ArrayList<String> getBinVal(){
36        ArrayList<String> binaryVal = new ArrayList<String>();
37        ArrayList<String> array = new ArrayList<String>();
38        Double num = number;
39        Double sol1, check; 
40
41        while( num > 0 ) {
42
43            sol1 = num/2;
44            check = sol1 - Math.floor(sol1);
45
46            if(check > 0) {
47                binaryVal.add("1");
48                num = sol1 - 0.5;
49            }
50
51            else {
52                binaryVal.add("0");
53                num = sol1;
54            }
55        }
56
57        while(binaryVal.size() < 4) {
58            binaryVal.add("0");
59        }
60
61        array = reverseArrayList(binaryVal);
62        return array;
63    }
64
65}
66
67class MainClass {
68    
69    public static void main(String[] args) {
70		
71      	//add the number in as a command line argument
72        Double num = Double.valueOf(args[0]);
73		
74      	//create an instance of Bin
75        Bin value = new Bin(num);
76		
77      	//print the binary value
78        System.out.println(value.getBinVal());
79    }
80}