Inserting variables into strings

Question

Im trying to insert the total_cost variable into the string in the last few lines without doing the ("its" + total_cost) method. Im trying to replicate the python {total_variable} method in java basically

    import java.util.Scanner;
    public class Decision2 {
        public static void main(String[] arrgs) {
            Scanner input = new Scanner(System.in);
            int ticket = 0;
            double total_cost = 0;
            System.out.println("How many tickets do you want to buy?");
            ticket = input.nextInt();
            if (ticket >= 5) {
                total_cost = total_cost + (10.95 * ticket);

            } else {
                total_cost = total_cost + (8.95 * ticket);


            }
            System.out.printf("The total cost is {total_cost}");
        }
    }

check this: https://stackoverflow.com/questions/6389827/string-variable-interpolation-java — Rafael, Sep 21 '22 at 16:26
Does this answer your question? [String variable interpolation Java](https://stackoverflow.com/questions/6389827/string-variable-interpolation-java) — starball, Aug 05 '23 at 00:18

score 1 · Answer 1 · edited Sep 21 '22 at 16:48

1

You can use java String Format such as

String foo = String.format("The total cost is %.2f",total_cost);

or if printing use such as

System.out.printf("The total cost is %.2f\n",total_cost);

edited Sep 21 '22 at 16:48

rzwitserloot

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answered Sep 21 '22 at 16:23

Mirco0

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You should never do that. In this case, `System.out.printf(format, params)` is the same as `System.out.println(String.format(format, params))` (add a \n for the newline), except shorter, and idiomatic. – rzwitserloot Sep 21 '22 at 16:24
Oh thank you for letting me know, I think this is a good option tho if you want to store in a String, I'll fix my answer – Mirco0 Sep 21 '22 at 16:26
Java code should use `%n` rather than `\n` for the line separator. – mernst Aug 04 '23 at 22:53

score 0 · Answer 2 · answered Aug 04 '23 at 22:55

You can use Java's String Templates feature. It is described in JEP 430, and it appears in JDK 21 as a preview feature. Here is an example use:

System.out.println(STR."The total cost is \{total_cost}.");

Java's string templates are more versatile, and much safer, than features in other languagues such as C#'s string interpolation and Python's f-strings. For example, string concatenation or interpolation makes SQL injection attacks possible:

String query = "SELECT * FROM Person p WHERE p.last_name = '" + name + "'";
ResultSet rs = conn.createStatement().executeQuery(query);

but this variant (from JEP 430) prevents SQL injection:

PreparedStatement ps = DB."SELECT * FROM Person p WHERE p.last_name = \{name}";
ResultSet rs = ps.executeQuery();

Inserting variables into strings

2 Answers2