這個示例的目的是模擬連結串列的實現方式，與ArrayList的底層實現相比查詢慢，增刪改快的優缺點。

package test;

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


	public void add(Object obj) {
		Node n = new Node();
		if(first==null) {
			
			n.setPrevious(null);
			n.setSelfObj(obj);
			n.setNext(null);
			
			first =n;
			last =n;
		}else {
			//直接往最後一個節點處新增
			n.setPrevious(last);
			n.setSelfObj(obj);
			n.setNext(null);
			
			last.setNext(n);
			last = n;
		}
		
		size++;
		
	}
	
	public int size() {
		return size;
	}
	
	
	public Object get(int index){
		//越界處理
		rangeCheck(index);
		Node temp=Node(index);
		
		return temp.getSelfObj();
	}
	
	public Node Node(int index) {
		rangeCheck(index);
		Node temp =null;
		if(first !=null) {
			temp = first;
			for(int i=0; i<index;i++) {
				temp=temp.getNext();
			}
	}
		return temp;
	}
	
	private void rangeCheck(int index)  {
		if (index < 0 || index >= size) {
			try {
				throw new Exception();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
	
	public void remove(int index) {
		rangeCheck(index);
		
		Node temp=Node(index);
		
		if(temp!=null) {
			Node up=temp.getPrevious();
			Node down = temp.getNext();
			
			if(down !=null) {
				down.setPrevious(up);
			}
			up.setNext(down);
			size--;
		}
		
	}
	
	
	public void add(int index, Object obj) {
		rangeCheck(index);
		//先獲取當前位置的節點
		Node currentNode = Node(index);
		//建立新節點
		Node temp = new Node();
		temp.setSelfObj(obj);
		
		if(currentNode!=null){		
			Node up= currentNode.getPrevious();
			up.setNext(temp);
			temp.setNext(currentNode);
			size++;
		}
		
	}
	
	public static void main(String[] arg) throws Exception {
		DesignLinkedList dll= new DesignLinkedList();
		//當只有"aaa"一個元素被新增的話，first 和 last的都是aaa, 節點的previous 和next的物件都是null
		dll.add("aaa"); 
		//第二個元素被新增之後，將當前last節點的next物件設定為ccc，然後然後將當前物件設定為last物件。		
		dll.add("cccc");
		dll.add("bbb");
		System.out.println(dll.size());
		System.out.println(dll.get(0));
		System.out.println(dll.get(1));
		dll.remove(2);
		System.out.println(dll.size);
		dll.add(1,"eee");
		System.out.println(dll.size);
		System.out.println(dll.get(1));
	}
	
	
}
 

package test;

//用來定義連結串列中的一個節點
public class Node {
	
	private Node previous;
	private Object selfObj;
	private Node next;
	
	public Node() {
		super();
	}
	public Node(Node previous, Object selfObj, Node next) {
		super();
		this.previous = previous;
		this.selfObj = selfObj;
		this.next = next;
	}
	public Node getPrevious() {
		return previous;
	}
	public void setPrevious(Node previous) {
		this.previous = previous;
	}
	public Object getSelfObj() {
		return selfObj;
	}
	public void setSelfObj(Object selfObj) {
		this.selfObj = selfObj;
	}
	public Node getNext() {
		return next;
	}
	public void setNext(Node next) {
		this.next = next;
	}

	
	
}