public class stringtodouble {
	public static void main(String args) {
    	String string = "1.23";
      	double decimal = Double.parseDouble(string);
    }
}

Double d = Double.valueOf(String str);

String str="122.202";
double dnum = Double.parseDouble(str);

String text = "12.34";
double value = Double.parseDouble(text);

Double myDouble = Double.parseDouble("23.5");