String.format() adding 2 blank spaces when arguments are empty strings

Question

I have this simple method that goes:

private String toJsonFormat(String name, Object value, boolean first) {
    value = value == null ? "" : value; 
    return String.format((first ? "" : ",") + "\"%1s\":\"%2s\"", name, value);
}

When my value argument is null, 2 blank spaces are added after the colon, instead of an empty string.

An example return value when null is passed:

"housenumber":"  "

How come?

It would be helpful if you'd provide a short but complete program demonstrating the problem. Also, unless the first part is really required to demonstrate the issue, you should remove that part of it. An ideal question for a problem like this contains a short but complete program with nothing but the issue at hand, along with a description of the expected and actual results. — Jon Skeet
– Jon Skeet, Commented Jan 2, 2015 at 11:45

Marko Topolnik · Accepted Answer · 2015-01-02 11:44:14Z

7

The format specifier

%2s

means that this field will be at least two characters wide, space-padded as necessary.

If what you meant is "the second string", then just write

%s

This will automatically give you the second argument because it is the second specifier you use. Same for %1s you have for the first argument.

answered Jan 2, 2015 at 11:44

Marko Topolnik

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1 Comment

Pearl Jade Over a year ago

Thank you, yes, I thought it had something to do with the order of the arguments :\

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