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NullCheat.java

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/*

# null

http://stackoverflow.com/questions/2707322/what-is-null-in-java

Has explicit bytecode support via the `aconst_null` and `ifnull` instructions.

*/

public class NullCheat {

public static String publicStaticString;

public static void main(String[] args) {

// Objects that are not explicitly initialized are initialized to `null`.

assert publicStaticString == null;

// Initialized objects are never null

assert new Object() != null;

/*

# NullPointerException

What you get for attempting to dereference a `null`.

Exists at the bytecode level: `invoke` instructions are documented to raise it.

*/

{

String s = null;

boolean fail = false;

try {

s.toLowerCase();

} catch (NullPointerException e) {

assert e.getClass() == NullPointerException.class;

fail = true;

}

assert fail;

}

}

}