自己动手实现LinkedList

public class YmhLinkedList {
private Node first;
private Node last;
int size;

public YmhLinkedList() {
}

//增
public void add(Object obj) {
if (first == null) {
first = new Node(obj);
last = first;
} else {
Node node = new Node(obj);
last.next = node;
node.prev = last;
last = node;
}
size++;
}

public void add(int index, Object obj) {
rangecheck(index);
Node node = new Node(obj);
Node temp = first;
for (int i = 0; i < index; i++) {
temp = temp.next;
}
if (temp.prev != null && temp.next != null) {
Node prevNode = temp.prev;
prevNode.next = node;
node.prev = prevNode;
node.next = temp;
temp.prev = node;
} else if (temp.prev == null) {
first = node;
temp.prev = node;
node.next = temp;
} else if (temp.next == null) {
temp.next = node;
node.prev = temp;
last = node;
}
size++;
}

//删
public Object remove(int index) {
rangecheck(index);
Node temp = first;
for (int i = 0; i < index; i++) {
temp = temp.next;
}
Object oldValue = temp.value;
if (temp.prev != null && temp.next != null) {
temp.prev.next = temp.next;
temp.next.prev = temp.prev;
temp = null;
} else if (temp.prev == null) {
first = temp.next;
temp.next.prev = null;
temp = null;
} else if (temp.next == null) {
last = temp.prev;
temp.prev.next = null;
temp = null;
}
size--;
return oldValue;
}

public boolean remove(Object obj) {
Node temp = first;
for (int i = 0; i < size; i++) {
if (obj.equals(temp.value)) {
remove(i);
return true;
}
temp = temp.next;
}
return false;
}

//改
public Object set(int index, Object obj) {
rangecheck(index);
Node temp = first;
for (int i = 0; i < index; i++) {
temp = temp.next;
}
Object oldValue = temp.value;
temp.value = obj;
return oldValue;
}

//查
public Object get(int index) {
rangecheck(index);
Node temp = first;
for (int i = 0; i < index; i++) {
temp = temp.next;
}
return temp.value;
}

private void rangecheck(int index) {
if (index < 0 || index > size) {
try {
throw new MyException();
} catch (MyException e) {
e.printStackTrace();
}
}
}

public int size() {
return size;
}

public boolean isEmpty() {
return size == 0;
}
}