how to convert from exponential(E) to ordinary float.

How about doing a little string reformating and using the direct method?

double d = 1.23e+4;

double d = Double.parseDouble("1.23e+4");

The value i have retrive from the database is 1.25E6 like that it  comes i want to set this to some bean ,that bean is added List, that List i used in jsp page for dispaly (Tag lib using)

I dont know where i want to change the value into float (the bean variable datatype is float )
and also i dont know how to change that !!!

Well then try this code:

public class Test {
	public static void main(String args[]) {
		String convertedStr = "1234.56E2";
		if(convertedStr.indexOf("E") != -1) {
		    convertedStr = convertedStr.substring(0,  convertedStr.indexOf("E") + 1) + "+" + convertedStr.substring(convertedStr.indexOf("E") + 1, convertedStr.length());
		}
		float fl = Float.parseFloat(convertedStr);
	}
}

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Or you can use NumberFormat object to format the numbers to your desired format.