Reuse a parameter in String.format?

Question

String hello = \"Hello\";

String.format(\"%s %s %s %s %s %s\", hello, hello, hello, hello, hello, hello);

hello hello hello hello hello hello 

Do

Answer 1

One common case for reusing an argument in String.format is with a separator (e.g. ";" for CSV or tab for console).

System.out.println(String.format("%s %2$s %s %2$s %s %n", "a", ";", "b", "c"));
// "a ; ; ; b"

This isn't the desired output. "c" doesn't appear anywhere.

You need to use the separator first (with %s) and only use the argument index (%2$s) for the following occurences :

System.out.println(String.format("%s %s %s %2$s %s %n", "a", ";", "b", "c"));
//  "a ; b ; c"

Spaces are added for readability and debugging. Once the format appears to be correct, spaces can be removed in the text editor:

System.out.println(String.format("%s%s%s%2$s%s%n", "a", ";", "b", "c"));
// "a;b;c"