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Head.java
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144 lines (107 loc) · 3.54 KB
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/*
* Copyright 1990-2010, Mark Little, University of Newcastle upon Tyne
* and others contributors as indicated
* by the @authors tag. All rights reserved.
* See the copyright.txt in the distribution for a
* full listing of individual contributors.
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU Lesser General Public License, v. 2.1.
* This program is distributed in the hope that it will be useful, but WITHOUT A
* 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,
* v.2.1 along with this distribution; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*
* (C) 1990-2010,
*/
package org.javasim.simset;
/*
* This class essentially defines the linked list manager used by the SIMSET
* class in SIMULA.
*/
// Thanks to Jim Bean for converting the C++SIM classes
/**
* @deprecated As of release 2.1 use Java's own linked lists.
*/
public class Head {
public Head () {
this.first = null;
this.last = null;
}
/**
* @return the first entry in the list.
*/
synchronized public Link first () {return first;};
/**
* @return the last entry in the list.
*/
synchronized public Link last () {return last;};
/**
* @param element make this the first element in the list.
*/
public void addFirst (Link element) {
if (element == null) // nothing to add
return;
if (element.inList()) // if in another list
element.out(); // pull it out.
if (first == null) { // Queue presently empty
first = element;
last = element;
element.theList = this;
} else {
element.precede(first);
first = element;
}
}
/**
* @param element make this the last entry in the list.
*/
public void addLast (Link element) {
if (element == null) // nothing to add
return;
if (element.inList()) // if in another list
element.out(); // pull it out.
if (last == null) { // Queue presently empty
first = element;
last = element;
element.theList = this;
} else {
element.follow(last);
last = element;
}
}
/**
* @return the number of elements in the list.
*/
synchronized public long cardinal () {
long numberOfElements = 0;
Link tempPtr = first;
while (tempPtr != null) {
numberOfElements++;
tempPtr = tempPtr.suc();
}
return numberOfElements;
}
/**
* @return <code>true</code> if the list is empty, <code>false</code> otherwise.
*/
synchronized public boolean empty () {return cardinal() == 0;}
/**
* Empty the list.
*/
synchronized public void clear () {
Link tempPtr = first, marker = null;
while (tempPtr != null) {
marker = tempPtr;
tempPtr = tempPtr.suc();
marker = null;
}
first = null;
last = null;
}
protected Link first;
protected Link last;
}