Java: Printing out an object for debugging

Question

I would like an easy way to print out a java object, or to say it another way, serialize an object as a string. I would like to see the values of all variables contained within the object, and if there are more objects (like a list or whatever) it should print out the stuff in that object as well. Basically, it would be something like JSON encoding, but JSON doesn't support infinity, and I need to see if there is infinity or NaN in one of the double or float values.

How can I do this?

If it's a class you wrote, just override the `ToString()` method appropriately. — Daniel DiPaolo, Apr 14 '11 at 20:34
I didn't write it. And that would take a long time to manually do it, even if I could. — Muhd, Apr 14 '11 at 20:35
possible duplicate of [Dumping a java object's properties](http://stackoverflow.com/questions/603013/dumping-a-java-objects-properties) — Chris Thompson, Apr 14 '11 at 20:38
@Amir see sec 2.4 of the spec - http://www.ietf.org/rfc/rfc4627.txt?number=4627 (NaN and infinity aren't supported by JSON officially) — Daniel DiPaolo, Apr 14 '11 at 20:43

score 17 · Accepted Answer · answered Apr 14 '11 at 20:39

17

You could use Gson to serialize to JSON as it now supports NaN and +/- infinity

answered Apr 14 '11 at 20:39

Daniel DiPaolo

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This works beautifully, way better than the reflection in the other answer. I used `Gson gson = new GsonBuilder().serializeSpecialFloatingPointValues().serializeNulls().create(); System.out.println(gson.toJson(obj));` which let me see nulls, NaN and infinity values. – Muhd Apr 19 '11 at 21:23
This doesn't work quite well with mocked objects or static variables – hasanac Dec 05 '17 at 08:25

lobster1234 · Answer 2 · 2013-06-17T08:07:28.693

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More often than not ToStringBuilder.reflectionToString(Object) works great. It wont work when doing Maps though.

edited Jun 17 '13 at 08:07

answered Apr 14 '11 at 20:39

lobster1234

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...which is a part of apache's commons-lang – MeBigFatGuy Apr 14 '11 at 20:40
the link appears to be broken. Please verify if it has been moved to a new location. – Shamim Hafiz - MSFT Jun 14 '13 at 19:16

Java: Printing out an object for debugging

2 Answers2