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NullCheat.java
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39 lines (30 loc) · 1.01 KB
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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;
}
}
}