source code Double class

package wclasses;

public class SampleDouble {
    public static void main(String att[])
    {

        // constructors
        Double d1= new Double(10.5);
        Double dd=new Double(10.5d);
        Double ds=new Double("10.5");

        // wrapper to primitive
        double pd1=d1.doubleValue();
        System.out.println(pd1);
        
        //primitive to string
        String s1=d1.toString();
        String s2=Double.toString(10.57f);
        System.out.println(s1);
        System.out.println(s2);
        
        //String to primitive
        double pd2=Double.parseDouble(s2);
        System.out.println(pd2);
        
        //String to wrapper object
        Double d2= new Double("10");
        Double d3=Double.valueOf("100");
        System.out.println(d2);
        System.out.println(d3);

        //wrapper to string
        String s3=d3.toString();
    }

}

output:
10.5
10.5
10.569999694824219
10.569999694824219
10.0
100.0