Getting default value for primitive types

Question

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 1

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 

Answer 2

It's possible to get the default value of any type by creating an array of one element and retrieving its first value.

private static <T> T getDefaultValue(Class<T> clazz) {     return (T) Array.get(Array.newInstance(clazz, 1), 0); } 

This way there is not need to take account for every possible primitive type, at the usually negligible cost of creating a one-element array.