Java MessageFormat cannot format

Question

Here is a string template read from file.

Dialogue: {0}
Dialogue: {1}

After I read it from file, I want to format this string using given array.

var sentences = arrayOf("hello", "world")
var template = File("file_path").readText()

template = MessageFormat.format(template, sentences)

print(template)

But I get output.

Dialogue: [Ljava.lang.String;@27c170f0
Dialogue: {1}

EDIT

If I put array elements one by one, I will get right output.

Because MessageFormat.format accept Object... and see sentences as one Object not an array of Object. In Kotlin not sure what to do... In Java it would be as simple as declaring sentences as an array. — AxelH
– AxelH, Commented Apr 27, 2018 at 12:37
Also, you need to assign the result of MessageFormat.format() to a variable and print that result. The code you posted can't produce the output you gave. — JB Nizet
– JB Nizet, Commented Apr 27, 2018 at 12:39

Lionel Briand · Accepted Answer · 2018-04-27 12:38:33Z

5

The sentence variable is an array and not multiple argument. You have to to put a * (spread operator) before to transform it into vararg.

MessageFormat.format(template, *sentences)

answered Apr 27, 2018 at 12:38

Lionel Briand

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Alex Romanov · Accepted Answer · 2018-04-27 12:58:57Z

1

You can use spread operator *:

MessageFormat.format(template, *sentences)

It will transform an array into vararg to match format method signature:

format(String pattern, Object... arguments)

From the docs:

When we call a vararg-function, we can pass arguments one-by-one, e.g. asList(1, 2, 3), or, if we already have an array and want to pass its contents to the function, we use the spread operator (prefix the array with *)

edited Apr 27, 2018 at 12:58

answered Apr 27, 2018 at 12:39

Alex Romanov

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2 Comments

CoXier Over a year ago

Thanks a lot. I do not know which answer should be accepted.You are both right.

Alex Romanov Over a year ago

@Lionel Briand answered a few seconds earlier, so it will be honest to accept his one :)

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