如何解析字符串以从中获取双精度值

Question

Help me please for the next problem:

There is String pattern, assume it's public final static variable. There is string where we search. There is class, simple wrapper to double

public class Wrapper {

    private double value;

    public double getValue() {
        return value;
    }

    public Wrapper(double value) {
        this.value = value;
    }
}

I need method

public Wrapper parse(String s, int index)

which returns Wrapper's object if string at the index is double number with maximum 2 digits after decimal point(if there is decimal point at all) and right after number ends there is String pattern after it For example for strings

String pattern = "money";
String search = "Giveme10.25moneyplease";

parse(search, 6) returns new Wrapper(10.25)

In other cases (index less then zero, greater then length of the string, substring that starts from index isn't number at all or it's double number but it contains more then 2 digits after decimal point or there is no string pattern after number) method must return null

And another method that differs only string pattern must be first and then double number with maximum 2 digits after decimal point and all other the same

String pattern = "money"
String s = "Ihavemoney10.50"

parse1(s, 5) returns new Wrapper(10.50)

Answer 1

You can use DecimalFormat along with ParsePosition like this

import java.text.DecimalFormat;
import java.text.ParsePosition;

public class TestP {

    public static void main(String[] args) {


        DecimalFormat decimalFormat = new DecimalFormat("00.##'money'");

        String search = "Giveme10.25moneyplease";

        int index = 6;
        //output 10.25
       Number number = decimalFormat.parse(search, new ParsePosition(index));

    if (number != null) {
        String s = number.toString();           
        if (s.contains(".") && s.length() > 5) {
            number = null;
        }
    }
    System.out.println(number);

    }

}