concatenate fields from array of Java objects

Question

I am a newbie to Java. I have an array of objects that have a string field. I can concatenate all of the strings into an string array by looping, but it's very inelegant.

int numObj = obj.length;
String[] strArray = new String[numObj];
for (int i = 0; i < numObj; i++) {
    strArray[i] = obj[i].strField;
}

Is there a way to concatenate that single field from all of the objects into a string array in one command? e.g.:

String[] strArray = (String[]){obj[].strField};

This doesn't work because obj[] is an array and so it doesn't have any fields, but using {obj.strField} doesn't work either, because there is no object called obj. BTW I really don't have to recast the field or do .toString() because it is already a string.

I looked at many, many of the other posts (but perhaps not enough?) related to this but I still could not figure this out. There are some that refer to converting an object array to a string array, but I don't think those posts mean converting a particular field in the objects, but the object itself, as an uncast type.

In MATLAB this would be trivial: strCellArray = {obj.strField}; would create a cell array of strings from all of the strFields in obj instantly.

Thanks for your help.

Sorry, you pretty much have to do the loop. This is an area where Java is a bit inelegant compared to some other languages. Java 8 or 9 or 10 may fix this. :-) — user949300
– user949300, Commented Jan 19, 2012 at 19:20

JB Nizet · Accepted Answer · 2012-01-19 19:22:03Z

7

What you did is the only way. You don't have to create a variable for the length of the array, though. And using public fields is, 99.99% of the times, a very bad idea:

String[] strings = new String[objects.length];
for (int i = 0; i < objects.length; i++) {
    strings[i] = objects[i].getStringField();
}

answered Jan 19, 2012 at 19:22

JB Nizet

694k94 gold badges1.3k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Mark Mikofski Over a year ago

Thanks for the tip on keeping fields private.

Collectives™ on Stack Overflow

concatenate fields from array of Java objects

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related