20162321王彪 2017-2018《程序设计与数据结构》第五周学习总结
学习目标
- 掌握Java Collections API的基本结构
- 理解Collection的抽象设计
- 掌握Collection实现的Java相关技术：继承/多态/泛型/接口
- 掌握栈的应用
- 掌握栈的实现（数组，链式）
- 分析Java Stack API
知识点总结
- 集合(collection)：线性的和非线性的；线性集合(linear collection)是集合中的元素排成一行。非线性集合是按不同于一行的方式来组织元素，例如按层次或是按网络的方式。
- 抽象(abstraction)在某些时候隐藏其细节。抽象数据类型(abstract data type,ADT)是其值和操作都没有在程序设计语言中定义的一种数据类型。它是抽象的，因为实现细节必须要定义，而且要对用户隐藏。
代码实现
- 用数组实现栈
public class ArrayStack<T> {
private final int DEFAULT_CAPACITY = 10;
private int count;
private T[] stack;
private T item;
public T pop () {
if (count==0){
System.out.println("Wrong num");
}
else {
item = stack[count-1];
stack[count-1]=null;
}
return item;
}
public T peek(){
if (count==0){
System.out.println("Wrong num");
}
else {
item = stack[count-1];
}
return item;
}
public boolean isEmpty(){
if (count==0)
return true;
else
return false;
}
public int size(){
return count;
}
public ArrayStack(){
count=0;
stack =(T[])(new Object[DEFAULT_CAPACITY]);
}
public void push(T element){
if (count==stack.length)
expandCapacity();
stack[count]=element;
count++;
}
public String toString(){
String result = "<top of stack>";
for (int index=count-1;index>=0;index--)
result += stack[index]+"\n";
return result+"<bottom of stack>";
}
private void expandCapacity(){
T[] larger = (T[])(new Object[stack.length*2]);
for (int index=0;index<stack.length;index++){
larger[index] = stack[index];
}
stack = larger;
}
-
peek()操作要注意当前栈是否是空。
-
用链表实现栈
public class LinkedStack<T> implements Stack<T>
{
private int count;
private LinearNode<T> top = new LinearNode<T>(null);//表头,数据为空
private LinearNode<T> end = new LinearNode<T>(null);//表尾
//----------------------------------------------------------------
// Creates an empty stack using the default capacity.
// ----------------------------------------------------------------
public LinkedStack() {
top.setNext(end);
count=0;
}
//----------------------------------------------------------------
// Removes the element at the top of this stack and returns a
// reference to it. Throws an EmptyCollectionException if the
// stack contains no elements.
// ----------------------------------------------------------------
public T pop() throws EmptyCollectionException {
if (count == 0) throw new EmptyCollectionException ("Pop operation failed. " + "The stack is empty.");
T result = top.getNext().getElement();
top.setNext(top.getNext().getNext());
top.setElement(null);
count--;
return result;
}
//----------------------------------------------------------------
// Returns a string representation of this stack.
// ----------------------------------------------------------------
public String toString() {
String result = "<top of stack>\n";
LinearNode current = top;
while (current != null) {
result += current.getElement() + "\n";
current = current.getNext();
}
return result + "<bottom of stack>";
}
//----------------------------------------------------------------
// The following methods are left as programming projects.
// ----------------------------------------------------------------
@Override
public int hashCode() {
return super.hashCode();
}
@Override
public void push(T element) {
LinearNode<T> now = new LinearNode<T>(element);//now是用来保存加入元素的节点类的实例
now.setNext(top.getNext());//指向top指向的对象
top.setNext(now);
count++;
}
@Override
public T peek() {
return top.getNext().getElement();
}
@Override
public boolean isEmpty() {
if (count==0)
return true;
else
return false;
}
@Override
public int size() {
return count;
}
public static void main(String[] args) {
LinkedStack mLinked = new LinkedStack();
mLinked.push(1);
System.out.println(mLinked.isEmpty());
}
}
//************************************************************
// LinearNode.java Java Foundations
// // Represents a node in a linked list.
// ************************************************************
class LinearNode<T> {
private LinearNode<T> next;
private T element;
//----------------------------------------------------------------
// Creates an empty node.
// ----------------------------------------------------------------
public LinearNode() {
next = null;
element = null; }
//----------------------------------------------------------------
// Creates a node storing the specified element.
// ---------------------------------------------------------------
public LinearNode (T elem) {
next = null;
element = elem; }
//----------------------------------------------------------------
// Returns the node that follows this one.
// ----------------------------------------------------------------
public LinearNode<T> getNext() {
return next;
}
//----------------------------------------------------------------
// Sets the node that follows this one.
// ----------------------------------------------------------------
public void setNext (LinearNode<T> node) {
next = node;
}
//----------------------------------------------------------------
// Returns the element stored in this node.
// ----------------------------------------------------------------
public T getElement() {
return element;
}
public void setElement (T elem) {
element = elem;
}
}
-
以上代码是我和刘先润一起写的，所以相同。我们的代码和书上的代码也有一些不同。我们最初定义了两个节点。一个头结点一个尾节点。在构造函数将头节点指向为节点。在操作中头结点和尾节点都不存储数据。(但是后来发现到时没什么作用，到时代码比之书上并不简洁)
-
Android演示Stack
-
我的思路用RecyclerView来完成此次app.
-
1.首先要使用RecyclerView就要先添加依赖
compile 'com.android.support:cardview-v7:21.0.3'
compile 'com.android.support:recyclerview-v7:21.0.3'
- 2.定义一个item
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="130dp"
android:gravity="center"
android:layout_margin="4dp"
android:textColor="#99000000"
android:textStyle="bold"
android:textSize="22sp"
android:background="@color/md_blue_100"
android:text="0"/>
</LinearLayout>
- 3.Activity布局
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="wb.is.besti.edu.cd.mystack.MainActivity">
<LinearLayout
android:id="@+id/liner"
android:layout_width="match_parent"
android:layout_height="60dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:layout_marginBottom="16dp">
<EditText
android:id="@+id/mtext"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<android.support.v7.widget.RecyclerView
android:id="@+id/list"
android:clipToPadding="false"
android:scrollbarStyle="outsideOverlay"
android:layout_below="@+id/liner"
android:layout_height="match_parent"
android:layout_width="wrap_content"></android.support.v7.widget.RecyclerView>
</RelativeLayout>
- 4.menu的布局
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item android:id="@+id/action_push"
android:title="PUSH"
android:orderInCategory="100"
app:showAsAction="always"></item>
<item
android:id="@+id/action_pop"
android:title="POP"
android:orderInCategory="100"
app:showAsAction="always"></item>
</menu>
- 5.Activity
public class MainActivity extends AppCompatActivity {
RecyclerView mRecyclerView;
SimpleAdapter mAdapter;
EditText mText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mText = (EditText)findViewById(R.id.mtext);
mRecyclerView = (RecyclerView)findViewById(R.id.list);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
mRecyclerView.addItemDecoration(new DividerItemDecoration(this,LinearLayoutManager.VERTICAL));
mAdapter = new SimpleAdapter(this);
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.setAdapter(mAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.popandpush,menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id==R.id.action_push){
mAdapter.push(mText.getText().toString());
return true;
}
if (id==R.id.action_pop){
mAdapter.remove(SimpleAdapter.LAST_POSITION);
return true;
}
return super.onOptionsItemSelected(item);
}
}
- 6.适配器Adapter
public class SimpleAdapter extends RecyclerView.Adapter<SimpleAdapter.SimpleViewHolder> {
public static int LAST_POSITION = -1;
private final Context mContext;
private MyStack<String> myStack;
public void push(String s){
myStack.push(s);
LAST_POSITION++;
}
public void remove(int positon){
if (myStack.size()==0){
}
if (myStack.size()!=0){
myStack.pop();
notifyItemRemoved(positon);
}
}
public static class SimpleViewHolder extends RecyclerView.ViewHolder{
public final TextView title;
public SimpleViewHolder(View view){
super(view);
title = (TextView)view.findViewById(R.id.title);
}
}
public SimpleAdapter(Context context){
mContext = context;
myStack = new MyStack<>();
}
@Override
public SimpleViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
final View view = LayoutInflater.from(mContext).inflate(R.layout.simple_item,parent,false);
return new SimpleViewHolder(view);
}
@Override
public int getItemCount() {
return myStack.size();
}
@Override
public void onBindViewHolder(SimpleViewHolder holder, int position) {
holder.title.setText(myStack.peek());
}
}
-
7.(非必须)添加分割线
-
效果图
-
RecyclerView是我在完成假期的工作记录APP时了解到的控件，RecyclerView只管回收与复用View，其他的你可以自己去设置。其高度的解耦，给予你充分的定制自由。进一步的加深使用时添加卫星菜单来实现isEmpty(),peek(),size()等操作及将界面进一步美化。
