How to create a String with String.format by taking parameters from a list

Question

I want to create a String with String.format like this String.format("Q1={}, Q2={}, Q3={}, Q4={}" list) from the values of a list that contains Integers.

private String createString(Player player){

List<Integer> answers= new ArrayList<>();
    answers.add(player.getQuestion1());
    answers.add(player.getQuestion2());
    answers.add(player.getQuestion3());
    answers.add(player.getQuestion4());
    answers.add(player.getQuestion5());
    answers.add(player.getQuestion6());
    answers.add(player.getQuestion7());
    answers.add(player.getQuestion8());
    answers.add(player.getQuestion9());
    answers.add(player.getQuestion10());
    return String.format("Q1={}, Q2={}, Q3={}, Q4={}, Q5={}, Q6={}, Q7={}, Q8={}, Q9={}, Q10={}", answers.stream().map(a -> a.toString());

}

Can you add more details to the problem, like what you have tried so far. — Jennis Vaishnav
– Jennis Vaishnav, Commented Oct 16, 2019 at 11:56

Naman · Accepted Answer · 2019-10-16 12:07:05Z

4

Something like the following using Collectors.joining with mapping as required witht index and answer :

return IntStream.range(0, answers.size())
            .mapToObj(idx -> String.format("Q%s = %s", idx + 1, answers.get(idx)))
            .collect(Collectors.joining(", "))

edited Oct 16, 2019 at 12:07

answered Oct 16, 2019 at 12:01

Naman

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Comments

Sweeper · Accepted Answer · 2019-10-16 12:03:41Z

1

String.format is not suitable for formatting a list. Usually, String.join is more suitable.

First, create a list of strings to be joined by commas:

List<String> strings = IntStream.rangeClosed(1, answers.size())
    .mapToObj(x -> "Q" + x + "=" + answers.get(x - 1))
    .collect(Collectors.toList());

Then, call String.join:

String result = String.join(", ", strings);

answered Oct 16, 2019 at 12:03

Sweeper

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Comments

f1sh · Accepted Answer · 2019-10-16 12:04:23Z

1

String.format doesn't work well for this example because you need exactly the amount of placeholders in your format as the list size. You are better off building your own String. But in case you want to stick to String.format:

Since String.format uses varargs (which is an array), you can simply use toArray(). Please note that the placeholders in the format cannot be {} but something like %d, %s and so on

return String.format("Q1=%s, Q2=%s, Q3=%s, Q4=%s, Q5=%s, ...", answers.toArray());

answered Oct 16, 2019 at 12:04

f1sh

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3 Comments

Naman Over a year ago

Q1, Q2 is manually appended there, the index of the question.

Naman Over a year ago

The number 1,2,3 in the with Q intuitively could be the index of the question.

f1sh Over a year ago

Yes, it is. But there are individual getters for each of the 10 questions anyways. If OP wants to hardcode the String, this is the syntactically correct way to pass a list of values to a varargs method.

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