Converting Between Strings and Numbers

Example

public class Main {
    public static void main(String[] args) {
        String qtyText = "3";
        String priceText = "249.50";
        int qty = Integer.parseInt(qtyText);
        double price = Double.parseDouble(priceText);
        boolean flag = Boolean.parseBoolean("true");
        long phone = Long.parseLong("9876543210");
        System.out.println(qty * price);
        System.out.println(flag + " " + phone);
    }
}

Output

748.5
true 9876543210

Example

public class Main {
    public static void main(String[] args) {
        int pin = 500081;
        String a = String.valueOf(pin);
        String b = Integer.toString(pin);
        String c = "" + pin;            // quick, works but less clear
        System.out.println(a.length() + " digits");
        System.out.println(b + c);
    }
}

Output

6 digits
500081500081

Example

If the text is not a valid number, parseInt throws a NumberFormatException. You will learn to handle exceptions in the medium level.

public class Main {
    public static void main(String[] args) {
        String age = "twenty";
        int value = Integer.parseInt(age);
        System.out.println(value);
    }
}

Output

Exception: java.lang.NumberFormatException: For input string: "twenty"