listbuffer.java

是一款用JAVA 编写的编译器 具有很强的编译功能

/*
 * Copyright 1999-2006 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package com.sun.tools.javac.util;

import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;

/** A class for constructing lists by appending elements. Modelled after
 *  java.lang.StringBuffer.
 *
 *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If
 *  you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
public class ListBuffer<A> implements Collection<A> {

    public static <T> ListBuffer<T> lb() {
	return new ListBuffer<T>();
    }

    /** The list of elements of this buffer.
     */
    public List<A> elems;

    /** A pointer pointing to the last, sentinel element of `elems'.
     */
    public List<A> last;

    /** The number of element in this buffer.
     */
    public int count;

    /** Has a list been created from this buffer yet?
     */
    public boolean shared;

    /** Create a new initially empty list buffer.
     */
    public ListBuffer() {
	clear();
    }

    public final void clear() {
	this.elems = new List<A>(null,null);
	this.last = this.elems;
	count = 0;
	shared = false;
    }

    /** Return the number of elements in this buffer.
     */
    public int length() {
	return count;
    }
    public int size() {
	return count;
    }

    /** Is buffer empty?
     */
    public boolean isEmpty() {
	return count == 0;
    }

    /** Is buffer not empty?
     */
    public boolean nonEmpty() {
	return count != 0;
    }

    /** Copy list and sets last.
     */
    private void copy() {
	List<A> p = elems = new List<A>(elems.head, elems.tail);
	while (true) {
	    List<A> tail = p.tail;
	    if (tail == null) break;
	    tail = new List<A>(tail.head, tail.tail);
	    p.setTail(tail);
	    p = tail;
	}
	last = p;
	shared = false;
    }

    /** Prepend an element to buffer.
     */
    public ListBuffer<A> prepend(A x) {
	elems = elems.prepend(x);
	count++;
	return this;
    }

    /** Append an element to buffer.
     */
    public ListBuffer<A> append(A x) {
	if (shared) copy();
	last.head = x;
	last.setTail(new List<A>(null,null));
	last = last.tail;
	count++;
	return this;
    }

    /** Append all elements in a list to buffer.
     */
    public ListBuffer<A> appendList(List<A> xs) {
	while (xs.nonEmpty()) {
	    append(xs.head);
	    xs = xs.tail;
	}
	return this;
    }

    /** Append all elements in a list to buffer.
     */
    public ListBuffer<A> appendList(ListBuffer<A> xs) {
	return appendList(xs.toList());
    }

    /** Append all elements in an array to buffer.
     */
    public ListBuffer<A> appendArray(A[] xs) {
	for (int i = 0; i < xs.length; i++) {
	    append(xs[i]);
	}
	return this;
    }

    /** Convert buffer to a list of all its elements.
     */
    public List<A> toList() {
	shared = true;
	return elems;
    }

    /** Does the list contain the specified element?
     */
    public boolean contains(Object x) {
	return elems.contains(x);
    }

    /** Convert buffer to an array
     */
    public <T> T[] toArray(T[] vec) {
	return elems.toArray(vec);
    }
    public Object[] toArray() {
	return toArray(new Object[size()]);
    }

    /** The first element in this buffer.
     */
    public A first() {
	return elems.head;
    }

    /** Remove the first element in this buffer.
     */
    public void remove() {
	if (elems != last) {
	    elems = elems.tail;
	    count--;
	}
    }

    /** Return first element in this buffer and remove
     */
    public A next() {
        A x = elems.head;
	remove();
	return x;
    }

    /** An enumeration of all elements in this buffer.
     */
    public Iterator<A> iterator() {
	return new Iterator<A>() {
	    List<A> elems = ListBuffer.this.elems;
	    public boolean hasNext() {
		return elems != last;
	    }
	    public A next() {
                if (elems == last)
                    throw new NoSuchElementException();
		A elem = elems.head;
		elems = elems.tail;
		return elem;
	    }
	    public void remove() {
		throw new UnsupportedOperationException();
	    }
	};
    }

    public boolean add(A a) {
        throw new UnsupportedOperationException();
    }
    public boolean remove(Object o) {
        throw new UnsupportedOperationException();
    }
    public boolean containsAll(Collection<?> c) {
        throw new UnsupportedOperationException();
    }
    public boolean addAll(Collection<? extends A> c) {
        throw new UnsupportedOperationException();
    }
    public boolean removeAll(Collection<?> c) {
        throw new UnsupportedOperationException();
    }
    public boolean retainAll(Collection<?> c) {
        throw new UnsupportedOperationException();
    }
}