algo/java/08_stack/SampleBrowser.java at master · open-source-backup/algo · GitHub

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package algo.lesson08;

/**

* 使用前后栈实现浏览器的前进后退。

* @author chinalwb

public class SampleBrowser {

public static void main(String[] args) {

SampleBrowser browser = new SampleBrowser();

browser.open("http://www.baidu.com");

browser.open("http://news.baidu.com/");

browser.open("http://news.baidu.com/ent");

browser.goBack();

browser.goForward();

browser.open("http://www.qq.com");

browser.goForward();

browser.goBack();

browser.goForward();

browser.goBack();

browser.checkCurrentPage();

}

private String currentPage;

private LinkedListBasedStack backStack;

private LinkedListBasedStack forwardStack;

public SampleBrowser() {

this.backStack = new LinkedListBasedStack();

this.forwardStack = new LinkedListBasedStack();

}

public void open(String url) {

if (this.currentPage != null) {

this.backStack.push(this.currentPage);

this.forwardStack.clear();

}

showUrl(url, "Open");

}

public boolean canGoBack() {

return this.backStack.size() > 0;

}

public boolean canGoForward() {

return this.forwardStack.size() > 0;

}

public String goBack() {

if (this.canGoBack()) {

this.forwardStack.push(this.currentPage);

String backUrl = this.backStack.pop();

showUrl(backUrl, "Back");

return backUrl;

}

System.out.println("* Cannot go back, no pages behind.");

return null;

}

public String goForward() {

if (this.canGoForward()) {

this.backStack.push(this.currentPage);

String forwardUrl = this.forwardStack.pop();

showUrl(forwardUrl, "Foward");

return forwardUrl;

}

System.out.println("** Cannot go forward, no pages ahead.");

return null;

}

public void showUrl(String url, String prefix) {

this.currentPage = url;

System.out.println(prefix + " page == " + url);

}

public void checkCurrentPage() {

System.out.println("Current page is: " + this.currentPage);

}

/**

* A LinkedList based Stack implementation.

public static class LinkedListBasedStack {

// public static void main(String[] args) {

// LinkedListBasedStack stack = new LinkedListBasedStack();

// stack.push("A");

// stack.push("B");

// stack.push("C");

// stack.pop();

// stack.push("D");

// stack.push("E");

// stack.pop();

// stack.push("F");

// stack.print();

//// String data = stack.getTopData();

//// System.out.println("Top data == " + data);

// }

private int size;

private Node top;

static Node createNode(String data, Node next) {

return new Node(data, next);

}

public void clear() {

this.top = null;

this.size = 0;

}

public void push(String data) {

Node node = createNode(data, this.top);

this.top = node;

this.size++;

}

public String pop() {

Node popNode = this.top;

if (popNode == null) {

System.out.println("Stack is empty.");

return null;

}

this.top = popNode.next;

if (this.size > 0) {

this.size--;

}

return popNode.data;

}

public String getTopData() {

if (this.top == null) {

return null;

}

return this.top.data;

}

public int size() {

return this.size;

}

public void print() {

System.out.println("Print stack:");

Node currentNode = this.top;

while (currentNode != null) {

String data = currentNode.getData();

System.out.print(data + "\t");

currentNode = currentNode.next;

}

System.out.println();

}

public static class Node {

private String data;

private Node next;

public Node(String data) {

this(data, null);

}

public Node(String data, Node next) {

this.data = data;

this.next = next;

}

public void setData(String data) {

this.data = data;

}

public String getData() {

return this.data;

}

public void setNext(Node next) {

this.next = next;

}

public Node getNext() {

return this.next;

}

algo/java/08_stack/SampleBrowser.java at master · open-source-backup/algo · GitHub

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