Convert String to double in Java

Question

How can I convert a String such as "12.34" to a double in Java?

Answer 1

Used this to convert any String number to double when u need int just convert the data type from num and num2 to int ; took all the cases for any string double with Eng:"Bader Qandeel"

public static double str2doubel(String str) {
    double num = 0;
    double num2 = 0;
    int idForDot = str.indexOf('.');
    boolean isNeg = false;
    String st;
    int start = 0;
    int end = str.length();

    if (idForDot != -1) {
        st = str.substring(0, idForDot);
        for (int i = str.length() - 1; i >= idForDot + 1; i--) {
            num2 = (num2 + str.charAt(i) - '0') / 10;
        }
    } else {
        st = str;
    }

    if (st.charAt(0) == '-') {
        isNeg = true;
        start++;
    } else if (st.charAt(0) == '+') {
        start++;
    }

    for (int i = start; i < st.length(); i++) {
        if (st.charAt(i) == ',') {
            continue;
        }
        num *= 10;
        num += st.charAt(i) - '0';
    }

    num = num + num2;
    if (isNeg) {
        num = -1 * num;
    }
    return num;
}

Answer 2

If you have problems in parsing string to decimal values, you need to replace "," in the number to "."

---

String number = "123,321";
double value = Double.parseDouble( number.replace(",",".") );

Answer 3

Using Double.parseDouble() without surrounding try/catch block can cause potential NumberFormatException had the input double string not conforming to a valid format.

Guava offers a utility method for this which returns null in case your String can't be parsed.

https://google.github.io/guava/releases/19.0/api/docs/com/google/common/primitives/Doubles.html#tryParse(java.lang.String)

Double valueDouble = Doubles.tryParse(aPotentiallyCorruptedDoubleString);

In runtime, a malformed String input yields null assigned to valueDouble

Answer 4

To convert a string back into a double, try the following

String s = "10.1";
Double d = Double.parseDouble(s);

The parseDouble method will achieve the desired effect, and so will the Double.valueOf() method.

Answer 5

Citing the quote from Robertiano above again - because this is by far the most versatile and localization adaptive version. It deserves a full post!

Another option:

DecimalFormat df = new DecimalFormat(); 
DecimalFormatSymbols sfs = new DecimalFormatSymbols();
sfs.setDecimalSeparator(','); 
df.setDecimalFormatSymbols(sfs);
double d = df.parse(number).doubleValue();

Answer 6

You can use Double.parseDouble() to convert a String to a double:

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

For your case it looks like you want:

double total = Double.parseDouble(jlbTotal.getText());
double price = Double.parseDouble(jlbPrice.getText());