Click here to watch in Youtube :
https://www.youtube.com/watch?v=QvwMV4Yk7sg&list=UUhwKlOVR041tngjerWxVccw

/*
 * Converting Strings to Numbers.
 */
public class ValueOfDemo
{

    public static void main(String[] args)
    {
        /*
         * The Number subclasses that wrap primitive numeric
         * types ( Byte, Integer, Double, Float, Long, and
         * Short) each provide a class method named valueOf
         * that converts a string to an object of that type
         */
        Integer integerObj = Integer.valueOf("100");
        System.out.println("integerObj    = " + integerObj);

        Double doubleObj = Double.valueOf("20.289");
        System.out.println("doubleObj = " + doubleObj);
    }
}