Getting default value for primitive types

java reflection guava
ripper234 picture ripper234 · May 23, 2010 · Viewed 38k times · Source

I have a Java primitive type at hand:

Class<?> c = int.class; // or long.class, or boolean.class

I'd like to get a default value for this class -- specifically, the value is assigned to fields of this type if they are not initialized. E.g., 0 for a number, false for a boolean.

Is there a generic way to do this? I tried this:

c.newInstance()

But I'm getting an InstantiationException, and not a default instance.

Answer

whiskeysierra picture whiskeysierra · May 23, 2010

The Guava Libraries already contains that:
http://guava-libraries.googlecode.com/svn/trunk/javadoc/com/google/common/base/Defaults.html

Calling defaultValue will return the default value for any primitive type (as specified by the JLS), and null for any other type.

Use it like so:

import com.google.common.base.Defaults;
Defaults.defaultValue(Integer.TYPE); //will return 0

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