edu.umd.cs.findbugs.ba.type.NullType Maven / Gradle / Ivy
/*
* Bytecode Analysis Framework
* Copyright (C) 2003,2004 University of Maryland
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package edu.umd.cs.findbugs.ba.type;
import org.apache.bcel.generic.ReferenceType;
/**
* Special type representing the null value. This is a type which is higher in
* the lattice than any object type, but lower than the overall Top type. It
* represents the type of the null value, which may logically be merged with any
* object type without loss of information.
*
* @author David Hovemeyer
* @see TypeAnalysis
* @see TypeFrame
* @see TypeMerger
*/
public class NullType extends ReferenceType implements ExtendedTypes {
private static final long serialVersionUID = 1L;
private static final NullType theInstance = new NullType();
private NullType() {
super(T_NULL, "");
}
@Override
public int hashCode() {
return System.identityHashCode(this);
}
@Override
public boolean equals(Object o) {
return o == this;
}
public static NullType instance() {
return theInstance;
}
}