247 lines
6.0 KiB
Java
247 lines
6.0 KiB
Java
import java.util.Iterator;
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/**
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* A list of bodies implemented as a linked list.
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* The number of elements of the list is not limited.
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*/
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public class BodyLinkedList implements Iterable<Body> {
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private int size = 0;
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private Item first;
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private Item last;
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/**
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* Initializes 'this' as an empty list.
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*/
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public BodyLinkedList() {
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first = null;
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last = null;
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}
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/**
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* Initializes 'this' as an independent copy of the specified list 'list'.
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* Calling methods of this list will not affect the specified list 'list'
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* and vice versa.
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* Precondition: list != null.
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*/
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public BodyLinkedList(BodyLinkedList list) {
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this.size = 0;
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for (Body b : list) {
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this.addLast(b);
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}
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}
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/**
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* Inserts the specified element 'body' at the beginning of this list.
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*/
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public void addFirst(Body body) {
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if (first == null) {
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first = new Item(body);
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last = first;
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} else {
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first.setPrev(new Item(body));
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first = first.prev;
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}
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size++;
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}
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/**
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* Appends the specified element 'body' to the end of this list.
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*/
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public void addLast(Body body) {
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if (last == null) {
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last = new Item(body);
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first = last;
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} else {
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last.setNext(new Item(body));
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last = last.next;
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}
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size++;
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}
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/**
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* Returns the last element in this list.
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* Returns 'null' if the list is empty.
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*/
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public Body getLast() {
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return (last != null) ? last.body : null;
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}
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/**
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* Returns the first element in this list.
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* Returns 'null' if the list is empty.
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*/
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public Body getFirst() {
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return (first != null) ? first.body : null;
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}
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/**
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* Retrieves and removes the first element in this list.
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* Returns 'null' if the list is empty.
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*/
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public Body pollFirst() {
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if (first == null) {
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return null;
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}
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Body b = first.body;
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first = first.next;
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if (first != null) first.setPrev(null);
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size--;
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return b;
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}
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/**
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* Retrieves and removes the last element in this list.
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* Returns 'null' if the list is empty.
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*/
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public Body pollLast() {
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if (last == null) {
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return null;
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}
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Body b = last.body;
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last = last.prev;
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if (last != null) last.setNext(null);
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size--;
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return b;
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}
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/**
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* Inserts the specified element 'body' at the specified position in this list.
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* Precondition: i >= 0 && i <= size().
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*/
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public void add(int i, Body body) {
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if (first == null || i == 0) {
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addFirst(body);
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return;
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} else if (i == size) {
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addLast(body);
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return;
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}
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Item item = first;
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for (int j = 0; j < i; j++) {
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item = item.next;
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}
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item.prev.setNext(new Item(body));
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item.setPrev(item.prev.next);
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size++;
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}
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private Body removeItem(Item item) {
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if (item == first) {
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first = item.next;
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if (first != null) first.setPrev(null);
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} else if (item == last) {
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last = item.prev;
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if (last != null) last.setNext(null);
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} else {
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item.next.setPrev(item.prev);
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}
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size--;
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return item.body;
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}
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/**
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* Returns the element at the specified position in this list.
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* Precondition: i >= 0 && i < size().
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*/
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public Body get(int i) {
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Item item;
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if (i < size / 2) {
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item = first;
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for (int j = 0; j < i; j++) {
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item = item.next;
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}
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} else {
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item = last;
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for (int j = size - 1; j > i; j--) {
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item = item.prev;
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}
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}
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return item.body;
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}
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/**
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* Returns the index of the first occurrence of the specified element in this list, or -1 if
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* this list does not contain the element.
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*/
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public int indexOf(Body body) {
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if (first == null) {
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return -1;
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}
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Item item = first;
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for (int i = 0; i < size; i++, item = item.next) {
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if (item.body == body) return i;
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}
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return -1;
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}
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/**
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* Removes all bodies of this list, which are colliding with the specified
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* body. Returns a list with all the removed bodies.
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*/
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public BodyLinkedList removeCollidingWith(Body body) {
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BodyLinkedList removed = new BodyLinkedList();
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for (Item item = first; item != null; item = item.next) {
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if (body != item.body && body.collidesWith(item.body)) {
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removed.addLast(this.removeItem(item));
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}
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}
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return removed;
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}
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/**
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* Returns the number of bodies in this list.
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*/
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public int size() {
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return size;
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}
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@Override
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public Iterator<Body> iterator() {
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return new Iterator<>() {
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Item ptr = first;
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boolean yieldedFirst = false;
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@Override
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public boolean hasNext() {
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return ptr != null && (!yieldedFirst || ptr.next != null);
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}
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@Override
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public Body next() {
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if (!yieldedFirst) {
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yieldedFirst = true;
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} else {
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ptr = ptr.next;
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}
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return ptr.body;
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}
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};
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}
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private static class Item {
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private final Body body;
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private Item prev;
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private Item next;
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public Item(Body body) {
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this.body = body;
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this.prev = null;
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this.next = null;
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}
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public void setPrev(Item prev) {
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this.prev = prev;
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if (prev != null) prev.next = this;
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}
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public void setNext(Item next) {
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this.next = next;
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if (next != null) next.prev = this;
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}
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}
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}
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