233 lines
6.5 KiB
Java
233 lines
6.5 KiB
Java
/*
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* Copyright (c) 2002, 2003, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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class List<A> {
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/** The first element of the list, supposed to be immutable.
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*/
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public A head;
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/** The remainder of the list except for its first element, supposed
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* to be immutable.
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*/
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public List<A> tail;
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/** Construct a list given its head and tail.
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*/
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public List(A head, List<A> tail) {
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this.tail = tail;
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this.head = head;
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}
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/** Construct an empty list.
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*/
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public List() {
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this(null, null);
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}
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/** Construct a list consisting of given element.
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*/
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public static <A> List<A> make(A x1) {
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return new List<A>(x1, new List<A>());
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}
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/** Construct a list consisting of given elements.
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*/
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public static <A> List<A> make(A x1, A x2) {
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return new List<A>(x1, new List<A>(x2, new List<A>()));
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}
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/** Construct a list consisting of given elements.
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*/
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public static <A> List<A> make(A x1, A x2, A x3) {
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return new List<A>(x1, new List<A>(x2, new List<A>(x3, new List<A>())));
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}
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/** Construct a list consisting all elements of given array.
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*/
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public static <A> List<A> make(A[] vec) {
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List<A> xs = new List<A>();
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for (int i = vec.length - 1; i >= 0; i--)
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xs = new List<A>(vec[i], xs);
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return xs;
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}
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/** Construct a list consisting of a given number of identical elements.
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* @param len The number of elements in the list.
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* @param init The value of each element.
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*/
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public static <A> List<A> make(int len, A init) {
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List<A> l = new List<A>();
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for (int i = 0; i < len; i++) l = new List<A>(init, l);
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return l;
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}
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/** Does list have no elements?
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*/
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public boolean isEmpty() {
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return tail == null;
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}
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/** Does list have elements?
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*/
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public boolean nonEmpty() {
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return tail != null;
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}
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/** Return the number of elements in this list.
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*/
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public int length() {
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List<A> l = this;
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int len = 0;
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while (l.tail != null) {
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l = l.tail;
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len++;
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}
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return len;
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}
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/** Prepend given element to front of list, forming and returning
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* a new list.
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*/
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public List<A> prepend(A x) {
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return new List<A>(x, this);
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}
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/** Prepend given list of elements to front of list, forming and returning
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* a new list.
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*/
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public List<A> prependList(List<A> xs) {
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if (this.isEmpty()) return xs;
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else if (xs.isEmpty()) return this;
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else return this.prependList(xs.tail).prepend(xs.head);
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}
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/** Reverse list, forming and returning a new list.
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*/
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public List<A> reverse() {
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List<A> rev = new List<A>();
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for (List<A> l = this; l.nonEmpty(); l = l.tail)
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rev = new List<A>(l.head, rev);
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return rev;
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}
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/** Append given element at length, forming and returning
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* a new list.
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*/
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public List<A> append(A x) {
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return make(x).prependList(this);
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}
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/** Append given list at length, forming and returning
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* a new list.
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*/
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public List<A> appendList(List<A> x) {
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return x.prependList(this);
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}
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/** Copy successive elements of this list into given vector until
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* list is exhausted or end of vector is reached.
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*/
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public A[] toArray(A[] vec) {
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int i = 0;
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List<A> l = this;
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while (l.nonEmpty() && i < vec.length) {
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vec[i] = l.head;
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l = l.tail;
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i++;
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}
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return vec;
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}
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/** Form a string listing all elements with given separator character.
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*/
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public String toString(String sep) {
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if (isEmpty()) {
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return "";
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} else {
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StringBuffer buf = new StringBuffer();
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buf.append(((Object)head).toString());
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for (List<A> l = tail; l.nonEmpty(); l = l.tail) {
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buf.append(sep);
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buf.append(((Object)l.head).toString());
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}
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return buf.toString();
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}
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}
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/** Form a string listing all elements with comma as the separator character.
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*/
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public String toString() {
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return toString(",");
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}
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/** Compute a hash code, overrides Object
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*/
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public int hashCode() {
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List<A> l = this;
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int h = 0;
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while (l.tail != null) {
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h = h * 41 + (head != null ? head.hashCode() : 0);
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l = l.tail;
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}
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return h;
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}
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/** Is this list the same as other list?
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*/
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public boolean equals(Object other) {
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return other instanceof List && equals(this, (List)other);
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}
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/** Are the two lists the same?
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*/
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public static boolean equals(List xs, List ys) {
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while (xs.tail != null && ys.tail != null) {
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if (xs.head == null) {
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if (ys.head != null) return false;
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} else {
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if (!xs.head.equals(ys.head)) return false;
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}
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xs = xs.tail;
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ys = ys.tail;
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}
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return xs.tail == null && ys.tail == null;
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}
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/** Does the list contain the specified element?
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*/
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public boolean contains(A x) {
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List<A> l = this;
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while (l.tail != null) {
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if (x == null) {
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if (l.head == null) return true;
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} else {
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if (x.equals(l.head)) return true;
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}
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l = l.tail;
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}
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return false;
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}
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}
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