前言
这里将参考 JDK 的 LinkedList 底层源码,模拟手写一个简易版的 LinkedList。
代码
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| public interface MyList<E> {
void add(E element);
E set(int index, E element);
E get(int index);
E remove(int index);
void clear();
int size();
}
|
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| public class MyLinkedList<E> implements MyList<E> {
private int size = 0;
private Node<E> first;
private Node<E> last;
public MyLinkedList() {
}
private void linkLast(E element) { Node<E> l = last; Node<E> newNode = new Node<>(l, element, null); last = newNode; if (l == null) { first = newNode; } else { l.next = newNode; } size++; }
private E unlink(Node<E> node) { E data = node.data; Node<E> prev = node.prev; Node<E> next = node.next;
if (prev == null) { first = next; } else { prev.next = next; node.prev = null; }
if (next == null) { last = prev; } else { next.prev = prev; node.next = null; }
node.data = null; size--; return data; }
private void checkElementIndex(int index) { if (!isElementIndex(index)) { throw new IndexOutOfBoundsException(); } }
private boolean isElementIndex(int index) { return index >= 0 && index < size; }
private Node<E> node(int index) { checkElementIndex(index); Node<E> cur = first; for (int i = 0; i < index; i++) { cur = cur.next; } return cur; }
@Override public void add(E element) { linkLast(element); }
@Override public E set(int index, E element) { Node<E> node = node(index); E oldData = node.data; node.data = element; return oldData; }
@Override public E get(int index) { Node<E> node = node(index); return node.data; }
@Override public E remove(int index) { Node<E> node = node(index); return unlink(node); }
@Override public void clear() { Node<E> cur = first; while (cur != null) { Node<E> next = cur.next; cur.prev = null; cur.next = null; cur.data = null; cur = next; } first = null; last = null; size = 0; }
@Override public int size() { return size; }
@Override public String toString() { StringBuilder stringBuilder = new StringBuilder(); stringBuilder.append("["); Node<E> cur = first; while (cur != null) { stringBuilder.append(cur.data); if (cur != last) { stringBuilder.append(", "); } cur = cur.next; } stringBuilder.append("]"); return stringBuilder.toString(); }
static class Node<E> {
E data;
Node<E> prev;
Node<E> next;
Node(Node<E> prev, E element, Node<E> next) { this.prev = prev; this.next = next; this.data = element; }
}
}
|
测试
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| public class MyLinkedListTest {
public static void main(String[] args) { MyLinkedList<Integer> list = new MyLinkedList<>(); list.add(13); list.add(12); list.add(11); list.add(14); list.add(17); list.add(15); list.add(18); System.out.println(list);
Integer value = list.get(5); System.out.println("value = " + value);
Integer oldValue = list.set(1, 23); System.out.println("oldValue = " + oldValue); System.out.println(list);
list.remove(1); list.remove(1); list.remove(1); System.out.println(list); System.out.println("size = " + list.size());
list.clear(); System.out.println(list); System.out.println("size = " + list.size()); }
}
|
输出结果:
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| [13, 12, 11, 14, 17, 15, 18] value = 15 oldValue = 12 [13, 23, 11, 14, 17, 15, 18] [13, 17, 15, 18] size = 4 [] size = 0
|