How to implement a Linked List in Java? [duplicate]

Answer 1

LinkedList in java works as like that:

There is a static class like this:

private static class Entry {
E element;
Entry next;
Entry previous;
Entry(E element, Entry next, Entry previous) {
    this.element = element;
    this.next = next;
    this.previous = previous;
}
}

LinkedList constructors:

public LinkedList() {
    header.next = header.previous = header;
}

public LinkedList(Collection c) {
this();
addAll(c);
}

addAll method:

public boolean addAll(Collection c) {
    return addAll(size, c);
}

You should check here:

private transient Entry header = new Entry(null, null, null);
private transient int size = 0;

private Entry addBefore(E e, Entry entry) {
Entry newEntry = new Entry(e, entry, entry.previous);
newEntry.previous.next = newEntry;
newEntry.next.previous = newEntry;
size++;
modCount++;
return newEntry;
}

private E remove(Entry e) {
if (e == header)
    throw new NoSuchElementException();

    E result = e.element;
e.previous.next = e.next;
e.next.previous = e.previous;
    e.next = e.previous = null;
    e.element = null;
size--;
modCount++;
    return result;
}

private Entry addBefore(E e, Entry entry) {
Entry newEntry = new Entry(e, entry, entry.previous);
newEntry.previous.next = newEntry;
newEntry.next.previous = newEntry;
size++;
modCount++;
return newEntry;
}

public boolean add(E e) {
addBefore(e, header);
    return true;
}