面向对象第八天：

回顾：

1. 接口：

   ​ 引用数据类型，interface定义，只能包含常量和抽象方法

   ​ 不能被实例化，需要被实现，实现类：必须重写所有抽象方法

   ​ 一个类可以实现多个接口，用逗号分隔，若又继承又实现时应先继承后实现

   ​ 接口可以继承接口

   ​ 意义：封装部分派生类所共有的属性和行为----实现多继承

   ​ 是一个标准、是一种规范

笔记：

1、多态：
方法(行为就是方法)也是多态；
(1)表现：
①同一个对象被造型为不同的类型时，有不同的功能
-----对象的多态：我、你、水…所有对象都是多态的(明天体会)
②特点：同一类型的引用指向不同对象时，有不同的实现
-----行为的多态：cut()、move()、getImage()、getScore()-所有的抽象方法都是多态的

人 p1 = new 理发师();
人 p2 = new 外科医生();

(2)向上造型/自动类型转换：seaobject 0 = new Battleship();
①超类型的引用指向派生类的对象
②能点出来什么，看引用的类型：p1.cut(); p2.cut();
③能造型成为的数据类型有2种：超类+所实现的接口

(3)强制类型转换，成功的条件只有如下两种：
①引用所指向的对象，就是该类型
②引用所指向的对象，实现了该接口或继承了该类

(4)强转时若不符合如上条件，则发生ClassCastException类型转换异常
建议：在强转之前先通过instanceof来判断引用的对象是否是该类型

package ooday08;
public class MultiTypeDemo {public static void main(String[] args){/*强制类型转换，成功的条件只有如下两种：①引用o所指向的对象(是Boo())，就是该类型(Boo类型) “数据类型 引用类型变量 = new 对象”     数据类型:Aoo	 引用:就是引用类型变量   指向:就是等号=   对象:new出来的对象Boo②引用所指向的对象，实现了该接口或继承了该类*/Aoo o = new Boo();	 //o的对象是BooBoo o1 = (Boo)o;     //①引用o所指向的对象,就是Boo类型。 【把o赋给Boo回报错  因为o是Aoo，大转小，需要强转，o的前边加(Boo)】Inter o2 = (Inter)o; //②引用所指向的对象,实现了Inter接口//Coo o3 = (Coo)o;  //-运行时ClassCastException类型转换异常if(o instanceof Coo){	//false,先判断Coo o4 = (Coo)o;    //再强转}else{System.out.println("o不是Coo类型");}/*System.out.println(o instanceof Boo);//trueSystem.out.println(o instanceof Inter);//trueSystem.out.println(o instanceof Coo);//false       */}
}interface Inter{}
class Aoo{}
class Boo extends Aoo implements Inter{}
class Coo extends Aoo{}

补充：

1. 接口可以继承多个接口：

   interface Inter1{void show();
   }
   interface Inter2{void test();
   }
   interface Inter3 extends Inter1,Inter2{void say();
   } 
   

2. 何时需要强转？

   ---- 想访问的属性/行为在超类中没有，必须强转，强转之前先instanceof判断

3. ArrayIndexOutOfBoundsException：数组下标越界异常

   NullPointerException：空指针异常

   ClassCastException：类型转换异常

4. 此图片在作业2、深水炸弹与潜艇的碰撞中会用的到：

面向对象第八天作业：

1、水雷入场：后半段
2、深水炸弹与潜艇的碰撞
3、画分和画命

1、水雷入场：后半段。。参考代码：

package cn.tedu.submarine;
import javax.swing.JFrame;
import javax.swing.JPanel; //1.
import java.awt.Graphics;
import java.util.Timer;
import java.util.TimerTask;
import java.util.Random;
import java.util.Arrays;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;/** 整个游戏世界  */
public class World extends JPanel { //2.public static final int WIDTH = 641;  /** 窗口的宽 */public static final int HEIGHT = 479; /** 窗口的高 *///如下这一堆为窗口中所显示的对象private Battleship ship = new Battleship(); //战舰private SeaObject[] submarines = {};        //潜艇(侦察潜艇、鱼雷潜艇、水雷潜艇)数组private Mine[] mines = {};                  //水雷数组private Bomb[] bombs = {};                  //深水炸弹数组/** 生成潜艇(侦察潜艇、鱼雷潜艇、水雷潜艇)对象 */public SeaObject nextSubmarine(){Random rand = new Random(); //随机数对象int type = rand.nextInt(20); //0到19if(type<10){ //0到9时，返回侦察潜艇对象return new ObserveSubmarine();}else if(type<15){ //10到14，返回鱼雷潜艇对象return new TorpedoSubmarine();}else{ //15到19时，返回水雷潜艇对象return new MineSubmarine();}}private int subEnterIndex = 0; //潜艇入场计数/** 潜艇(侦察潜艇、鱼雷潜艇、水雷潜艇)入场 */public void submarineEnterAction(){ //每10毫秒走一次subEnterIndex++; //每10毫秒增1if(subEnterIndex%40==0) { //每400(40*10)毫秒走一次SeaObject obj = nextSubmarine(); //获取潜艇对象submarines = Arrays.copyOf(submarines,submarines.length+1); //扩容submarines[submarines.length-1] = obj; //将obj添加到submarines的最后一个元素上}}private int mineEnterIndex = 0; //水雷入场计数/** 水雷入场 */public void mineEnterAction(){ //每10毫秒走一次mineEnterIndex++; //每10毫秒增1if(mineEnterIndex%100==0){ //每1秒(100*10)走一次for(int i=0;i<submarines.length;i++){ //遍历所有潜艇if(submarines[i] instanceof MineSubmarine){ //若潜艇为水雷潜艇MineSubmarine ms = (MineSubmarine)submarines[i]; //将潜艇强转为水雷潜艇类型Mine obj = ms.shootMine(); //获取水雷对象mines = Arrays.copyOf(mines,mines.length+1); //扩容mines[mines.length-1] = obj; //将obj添加到最后一个元素上}}}}/** 海洋对象移动 */public void moveAction(){ //每10毫秒走一次for(int i=0;i<submarines.length;i++){ //遍历所有潜艇submarines[i].move(); //潜艇移动}for(int i=0;i<mines.length;i++){ //遍历所有水雷mines[i].move(); //水雷移动}for(int i=0;i<bombs.length;i++){ //遍历所有深水炸弹bombs[i].move(); //深水炸弹移动}}/** 删除越界的海洋对象 */public void outOfBoundsAction(){ //每10毫秒走一次for(int i=0;i<submarines.length;i++){ //遍历所有潜艇if(submarines[i].isOutOfBounds()){ //越界了submarines[i] = submarines[submarines.length-1]; //将越界潜艇替换为最后一个元素submarines = Arrays.copyOf(submarines,submarines.length-1); //缩容(缩掉最后一个元素)}}for(int i=0;i<mines.length;i++){ //遍历所有水雷if(mines[i].isOutOfBounds()){ //越界了mines[i] = mines[mines.length-1]; //将越界水雷替换为最后一个元素mines = Arrays.copyOf(mines,mines.length-1); //缩容(缩掉最后一个元素)}}for(int i=0;i<bombs.length;i++){ //遍历所有深水炸弹if(bombs[i].isOutOfBounds()){ //越界了bombs[i] = bombs[bombs.length-1]; //将越界炸弹替换为最后一个元素bombs = Arrays.copyOf(bombs,bombs.length-1); //缩容(缩掉最后一个元素)}}}/** 启动程序的执行 */public void action(){KeyAdapter k = new KeyAdapter() { //不要求掌握/** 重写keyReleased()按键抬起事件 */public void keyReleased(KeyEvent e) { //当按键抬起时会自动触发--不要求掌握if(e.getKeyCode()==KeyEvent.VK_SPACE){ //若抬起的是空格键--不要求掌握Bomb obj = ship.shoot(); //获取深水炸弹对象bombs = Arrays.copyOf(bombs,bombs.length+1); //扩容bombs[bombs.length-1] = obj; //将obj添加到bombs的最后一个元素上}if(e.getKeyCode()==KeyEvent.VK_LEFT){ //若抬起的是左键头--不要求掌握ship.moveLeft(); //战舰左移}if(e.getKeyCode()==KeyEvent.VK_RIGHT){ //若抬起的是右键头--不要求掌握ship.moveRight(); //战舰右移}}};this.addKeyListener(k); //不要求掌握Timer timer = new Timer(); //定时器对象int interval = 10; //定时间隔(以毫秒为单位)timer.schedule(new TimerTask() {public void run() { //定时干的事(每10毫秒自动发生)submarineEnterAction(); //潜艇(侦察潜艇、鱼雷潜艇、水雷潜艇)入场mineEnterAction();      //水雷入场moveAction();           //海洋对象移动outOfBoundsAction();    //删除越界的海洋对象repaint();              //重画(重新调用paint()画)}}, interval, interval); //定时计划}/** 重写paint()画  g:画笔 */public void paint(Graphics g){ //每10毫秒走一次Images.sea.paintIcon(null,g,0,0); //画海洋图ship.paintImage(g); //画战舰for(int i=0;i<submarines.length;i++){ //遍历潜艇数组submarines[i].paintImage(g); //画潜艇}for(int i=0;i<mines.length;i++){mines[i].paintImage(g);}for(int i=0;i<bombs.length;i++){bombs[i].paintImage(g);}}public static void main(String[] args) {JFrame frame = new JFrame(); //3.World world = new World();world.setFocusable(true);frame.add(world);frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setSize(WIDTH+16, HEIGHT+39);frame.setLocationRelativeTo(null);frame.setVisible(true); //1)设置窗口可见  2)尽快调用paint()方法world.action(); //启动程序的执行}
}//注:其余类没有变化，此处省略

2、深水炸弹与潜艇的碰撞。。参考代码：

package day08;
import javax.swing.ImageIcon;
import java.awt.Graphics;
import java.util.Random;
//海洋对象
public abstract class SeaObject {public static final int LIVE = 0;public static final int DEAD = 1;protected int state = LIVE; //当前状态protected int width;protected int height;protected int x;protected int y;protected int speed;public SeaObject(int width,int height){this.width = width;this.height = height;x = -width;Random rand = new Random();y = rand.nextInt(World.HEIGHT-height-150)+150;speed = rand.nextInt(3)+1;}public SeaObject(int width,int height,int x,int y,int speed){this.width = width;this.height = height;this.x = x;this.y = y;this.speed = speed;}public abstract void move();public abstract ImageIcon getImage();public boolean isLive(){return state==LIVE;}public boolean isDead(){return state==DEAD;}public void paintImage(Graphics g){if(isLive()){this.getImage().paintIcon(null,g,x,y);}}/** 检测潜艇越界 */public boolean isOutOfBounds(){return x>= World.WIDTH; //x>=窗口宽，即为越界了}/** 检测碰撞 */public boolean isHit(SeaObject other){//假设this指代潜艇，other指代炸弹int x1 = this.x-other.width;  //x1:潜艇的x-炸弹的宽int x2 = this.x+this.width;   //x2:潜艇的x+潜艇的宽int y1 = this.y-other.height; //y1:潜艇的y-炸弹的高int y2 = this.y+this.height;  //y2:潜艇的y+潜艇的高int x = other.x; //x:炸弹的xint y = other.y; //y:炸弹的yreturn x>=x1 && x<=x2&&y>=y1 && y<=y2; //x在x1与x2之间，并且，y在y1与y2之间，即为撞上了}/** 海洋对象去死 */public void goDead(){state = DEAD; //将状态修改为DEAD死了的}
}package day08;
import javax.swing.ImageIcon;
//战舰
public class Battleship extends SeaObject {private int life;public Battleship(){super(66,26,270,124,20);life = 5;}public void step(){System.out.println("战舰移动");}public ImageIcon getImage(){return Images.battleship;}public Bomb shoot(){return new Bomb(this.x,this.y);}public void moveLeft(){x-=speed;}public void moveRight(){x+=speed;}public void addLife(int num){life += num;}
}package day08;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Graphics;
import java.util.Arrays;
import java.util.Random;
import java.util.Timer;
import java.util.TimerTask;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
//整个游戏世界
public class World extends JPanel {public static final int WIDTH = 641;public static final int HEIGHT = 479;private Battleship ship = new Battleship(); //战舰private SeaObject[] submarines = {}; //潜艇(侦察潜艇、鱼雷潜艇、水雷潜艇)private Mine[] mines = {}; //水雷private Bomb[] bombs = {}; //深水炸弹/** 随机生成潜艇 */public SeaObject nextSubmarine(){Random rand = new Random();int type = rand.nextInt(20);if(type<10){return new ObserveSubmarine();}else if(type<15){return new TorpedoSubmarine();}else{return new MineSubmarine();}}private int subEnterIndex = 0;/** 潜艇入场 */public void submarineEnterAction(){ //每10毫秒走一次subEnterIndex++;if(subEnterIndex%40==0){ //每40毫秒SeaObject obj = nextSubmarine();submarines = Arrays.copyOf(submarines,submarines.length+1);submarines[submarines.length-1] = obj;}}private int mineEnterIndex = 0;/** 雷(鱼雷、水雷)入场 */public void MineEnterAction(){mineEnterIndex++;if(mineEnterIndex%100==0){for(int i=0;i<submarines.length;i++){if(submarines[i] instanceof MineSubmarine){MineSubmarine ms = (MineSubmarine)submarines[i];Mine obj = ms.shootMine();mines = Arrays.copyOf(mines,mines.length+1);mines[mines.length-1] = obj;}}}}/** 海洋对象移动 */public void moveAction(){for(int i=0;i<submarines.length;i++){submarines[i].move();}for(int i=0;i<mines.length;i++){mines[i].move();}for(int i=0;i<bombs.length;i++){bombs[i].move();}}/** 删除越界的对象 */public void outOfBoundsAction(){for(int i=0;i<submarines.length;i++){if(submarines[i].isOutOfBounds() || submarines[i].isDead()){submarines[i] = submarines[submarines.length-1];submarines = Arrays.copyOf(submarines,submarines.length-1);}}for(int i=0;i<mines.length;i++){if(mines[i].isOutOfBounds() || mines[i].isDead()){mines[i] = mines[mines.length-1];mines = Arrays.copyOf(mines,mines.length-1);}}for(int i=0;i<bombs.length;i++){if(bombs[i].isOutOfBounds() || bombs[i].isDead()){bombs[i] = bombs[bombs.length-1];bombs = Arrays.copyOf(bombs,bombs.length-1);}}}private int score = 0; //玩家得分//深水炸弹与潜艇的碰撞public void bombBangAction(){for(int i=0;i<bombs.length;i++){Bomb b = bombs[i];for(int j=0;j<submarines.length;j++){SeaObject s = submarines[j];if(b.isLive() && s.isLive() && s.isHit(b)){b.goDead();s.goDead();if(s instanceof EnemyScore){EnemyScore es = (EnemyScore)s;score += es.getScore();}if(s instanceof EnemyLife){EnemyLife ea = (EnemyLife)s;int num = ea.getLife();ship.addLife(num);}}}}}/** 启动程序的运行 */public void action(){KeyAdapter k = new KeyAdapter(){public void keyPressed(KeyEvent e) {if(e.getKeyCode() == KeyEvent.VK_SPACE){Bomb obj = ship.shoot(); //深水炸弹入场bombs = Arrays.copyOf(bombs,bombs.length+1);bombs[bombs.length-1] = obj;}if(e.getKeyCode() == KeyEvent.VK_LEFT){ship.moveLeft();}if(e.getKeyCode() == KeyEvent.VK_RIGHT){ship.moveRight();}}};this.addKeyListener(k);Timer timer = new Timer();int interval = 10;timer.schedule(new TimerTask() {public void run() {submarineEnterAction(); //潜艇(侦察、水雷、鱼雷)入场MineEnterAction();      //水雷入场moveAction();           //海洋对象移动outOfBoundsAction();    //删除越界的对象bombBangAction();       //深水炸弹与潜艇的碰撞repaint();}}, interval, interval);}public void paint(Graphics g){Images.sea.paintIcon(null,g,0,0); //画海洋图ship.paintImage(g);for(int i=0;i<submarines.length;i++){submarines[i].paintImage(g);}for(int i=0;i<mines.length;i++){mines[i].paintImage(g);}for(int i=0;i<bombs.length;i++){bombs[i].paintImage(g);}}public static void main(String[] args) {JFrame frame = new JFrame();World world = new World();world.setFocusable(true);frame.add(world);frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setSize(WIDTH+16, HEIGHT+39);frame.setLocationRelativeTo(null);frame.setVisible(true);world.action();}
}//注:其余类没有变化，此处省略

3、画分和画命。。参考代码：

package day08;
import javax.swing.ImageIcon;
//战舰
public class Battleship extends SeaObject {private int life;public Battleship(){super(66,26,270,124,20);life = 5;}public void step(){System.out.println("战舰移动");}public ImageIcon getImage(){return Images.battleship;}public Bomb shoot(){return new Bomb(this.x,this.y);}public void moveLeft(){x-=speed;}public void moveRight(){x+=speed;}public void addLife(int num){life += num;}public int getLife(){return life;}
}package day08;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Graphics;
import java.util.Arrays;
import java.util.Random;
import java.util.Timer;
import java.util.TimerTask;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
//整个游戏世界
public class World extends JPanel {public static final int WIDTH = 641;public static final int HEIGHT = 479;private Battleship ship = new Battleship(); //战舰private SeaObject[] submarines = {}; //潜艇(侦察潜艇、鱼雷潜艇、水雷潜艇)private Mine[] mines = {}; //水雷private Bomb[] bombs = {}; //深水炸弹/** 随机生成潜艇 */public SeaObject nextSubmarine(){Random rand = new Random();int type = rand.nextInt(20);if(type<10){return new ObserveSubmarine();}else if(type<15){return new TorpedoSubmarine();}else{return new MineSubmarine();}}private int subEnterIndex = 0;/** 潜艇入场 */public void submarineEnterAction(){ //每10毫秒走一次subEnterIndex++;if(subEnterIndex%40==0){ //每40毫秒SeaObject obj = nextSubmarine();submarines = Arrays.copyOf(submarines,submarines.length+1);submarines[submarines.length-1] = obj;}}private int mineEnterIndex = 0;/** 雷(鱼雷、水雷)入场 */public void MineEnterAction(){mineEnterIndex++;if(mineEnterIndex%100==0){for(int i=0;i<submarines.length;i++){if(submarines[i] instanceof MineSubmarine){MineSubmarine ms = (MineSubmarine)submarines[i];Mine obj = ms.shootMine();mines = Arrays.copyOf(mines,mines.length+1);mines[mines.length-1] = obj;}}}}/** 海洋对象移动 */public void moveAction(){for(int i=0;i<submarines.length;i++){submarines[i].move();}for(int i=0;i<mines.length;i++){mines[i].move();}for(int i=0;i<bombs.length;i++){bombs[i].move();}}/** 删除越界的对象 */public void outOfBoundsAction(){for(int i=0;i<submarines.length;i++){if(submarines[i].isOutOfBounds() || submarines[i].isDead()){submarines[i] = submarines[submarines.length-1];submarines = Arrays.copyOf(submarines,submarines.length-1);}}for(int i=0;i<mines.length;i++){if(mines[i].isOutOfBounds() || mines[i].isDead()){mines[i] = mines[mines.length-1];mines = Arrays.copyOf(mines,mines.length-1);}}for(int i=0;i<bombs.length;i++){if(bombs[i].isOutOfBounds() || bombs[i].isDead()){bombs[i] = bombs[bombs.length-1];bombs = Arrays.copyOf(bombs,bombs.length-1);}}}private int score = 0; //玩家得分//深水炸弹与潜艇的碰撞public void bombBangAction(){for(int i=0;i<bombs.length;i++){Bomb b = bombs[i];for(int j=0;j<submarines.length;j++){SeaObject s = submarines[j];if(b.isLive() && s.isLive() && s.isHit(b)){b.goDead();s.goDead();if(s instanceof EnemyScore){EnemyScore es = (EnemyScore)s;score += es.getScore();}if(s instanceof EnemyLife){EnemyLife ea = (EnemyLife)s;int num = ea.getLife();ship.addLife(num);}}}}}/** 启动程序的运行 */public void action(){KeyAdapter k = new KeyAdapter(){public void keyPressed(KeyEvent e) {if(e.getKeyCode() == KeyEvent.VK_SPACE){Bomb obj = ship.shoot(); //深水炸弹入场bombs = Arrays.copyOf(bombs,bombs.length+1);bombs[bombs.length-1] = obj;}if(e.getKeyCode() == KeyEvent.VK_LEFT){ship.moveLeft();}if(e.getKeyCode() == KeyEvent.VK_RIGHT){ship.moveRight();}}};this.addKeyListener(k);Timer timer = new Timer();int interval = 10;timer.schedule(new TimerTask() {public void run() {submarineEnterAction(); //潜艇(侦察、水雷、鱼雷)入场MineEnterAction();      //水雷入场moveAction();           //海洋对象移动outOfBoundsAction();    //删除越界的对象bombBangAction();       //深水炸弹与潜艇的碰撞repaint();}}, interval, interval);}public void paint(Graphics g){Images.sea.paintIcon(null,g,0,0); //画海洋图ship.paintImage(g);for(int i=0;i<submarines.length;i++){submarines[i].paintImage(g);}for(int i=0;i<mines.length;i++){mines[i].paintImage(g);}for(int i=0;i<bombs.length;i++){bombs[i].paintImage(g);}g.drawString("SCORE: "+score,200,50);g.drawString("LIFE: "+ship.getLife(),400,50);}public static void main(String[] args) {JFrame frame = new JFrame();World world = new World();world.setFocusable(true);frame.add(world);frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setSize(WIDTH+16, HEIGHT+39);frame.setLocationRelativeTo(null);frame.setVisible(true);world.action();}
}//注:其余类没有变化，此处省略