java通过链表实现队列,先进先出

节点类

package queue.demo;

public class Node {

private Object data;
private Node nextNode;
private Node prevNode;

public Node(Object data) {
super();
this.data = data;
    }

public Node(Object data, Node prevNode, Node nextNode) {
super();
this.data = data;
this.nextNode = nextNode;
this.prevNode = prevNode;
    }

public Node getNextNode() {
return nextNode;
    }

public void setNextNode(Node nextNode) {
this.nextNode = nextNode;
    }

public Object getData() {
return data;
    }

public void setData(Object data) {
this.data = data;
    }

public Node getPrevNode() {
return prevNode;
    }

public void setPrevNode(Node prevNode) {
this.prevNode = prevNode;
    }

}

队列类

package queue.demo;

public class Queue {

int length = 5;
int size = 0;

    Node first;
    Node last;

// 入队
public void add(String value) {
if (size == length) {
            System.out.println("队列以满,无法添加");
return;
        }
        Node newNode = new Node(value, last, null);
        Node temp = last;
        last = newNode;
if (temp == null) {
            first = newNode;
        } else {
            temp.setNextNode(newNode);
        }
        size++;
    }

// 出队,先进先出
public String removeFirst() {
if (size == 0) {
            System.out.println("空队列,无法出队");
return null;
        }
        Node temp = first;
        first = first.getNextNode();
        size--;
return (String) temp.getData();

    }

}

执行测试类

package queue.demo;

public class Main {

    public static void main(String[] args) {
        Queue q = new Queue();
        q.add("a");
        System.out.println("进队a");
        q.add("b");
        System.out.println("进队b");
        q.add("c");
        System.out.println("进队c");
        q.add("d");
        System.out.println("进队d");
        q.add("e");
        System.out.println("进队e");
        q.add("f");
        System.out.println("进队f");
        System.out.println("出队: " + q.removeFirst());
        System.out.println("出队: " + q.removeFirst());
        System.out.println("出队: " + q.removeFirst());
        System.out.println("出队: " + q.removeFirst());
        System.out.println("出队: " + q.removeFirst());
        System.out.println("出队: " + q.removeFirst());

    }

}

执行结果

进队a
进队b
进队c
进队d
进队e
队列以满,无法添加
进队f
出队: a
出队: b
出队: c
出队: d
出队: e
空队列,无法出队
出队: null