每日要点
this的小用法
用this调用类其他的构造器
public Fraction(int num, int den) {
this.num = num;
this.den = den;
this.normalize();
this.simplify();
}
public Fraction(double val) {
this((int) (val * 10000), 10000);
}
短除法
短除法 求两个数的最大公约数
private int gcd(int x, int y) {
if (x > y) {
return gcd(y, x);
}
else if (y % x != 0) {
return gcd(y % x, x);
}
else {
return x;
}
}
枚举
枚举 : 定义符号常量的最佳方式
如果一个变量的值只有有限个选项通常都可以考虑使用枚举类型
看如下例题:
性别的枚举:
public enum Gender {
MALE, FEMALE, UNKNOWN;
}
上下左右的枚举:
public enum Direction {
UP, RIGHT, DOWN, LEFT;
}
昨天作业讲解
- 1.写一个类 描述 数学上的分数 提供分数的加减乘除的运算 化简
分数类:
/**
* 分数 (有理数)
* @author Kygo
* @since 0.1
*/
public class Fraction {
private int num;
private int den;
/**
* 构造器 : 指定分子和分母创建分数对象
* @param num 分子
* @param den 分母
*/
public Fraction(int num, int den) {
this.num = num;
this.den = den;
this.normalize();
this.simplify();
}
/**
* 构造器
* @param val 小数
*/
// 用this调用类其他的构造器
public Fraction(double val) {
this((int) (val * 10000), 10000);
}
/**
* 加法
* @param other 另一个分数
* @return 分数相加结果对象
*/
public Fraction add(Fraction other) {
return new Fraction(num * other.den + other.num * den, den * other.den);
}
/**
* 减法
* @param other 另一个分数
* @return 分数相减结果对象
*/
public Fraction sub(Fraction other) {
return new Fraction(num * other.den - other.num * den, den * other.den);
}
/**
* 乘法
* @param other 另一个分数
* @return 分数相乘结果对象
*/
public Fraction mul(Fraction other) {
return new Fraction(num * other.num, den * other.den);
}
/**
* 除法
* @param other 另一个分数
* @return 分数相除结果对象
*/
public Fraction div(Fraction other) {
return new Fraction(num * other.den, den * other.num);
}
/**
* 正规负号化方法
*/
public void normalize() {
if (den < 0) {
num = -num;
den = -den;
}
}
/**
* 分数化简
*/
public void simplify() {
if (num != 0) {
int x = num < 0 ? -num : num;
int y = Math.abs(den);
int factor = gcd(x, y);
if (factor > 1) {
num /= factor;
den /= factor;
}
}
}
@Override
public String toString() {
if (num == 0) {
return "0";
}
else if (den == 1) {
return "" + num;
}
else {
return num + "/" + den;
}
}
// 短除法 求两个数的最大公约数
private int gcd(int x, int y) {
if (x > y) {
return gcd(y, x);
}
else if (y % x != 0) {
return gcd(y % x, x);
}
else {
return x;
}
}
}
测试类:
Fraction f1 = new Fraction(-2, -3);
System.out.println(f1);
Fraction f2 = new Fraction(0.75);
System.out.println(f2);
System.out.println(f1.add(f2));
System.out.println(f1.sub(f2));
System.out.println(f1.mul(f2));
System.out.println(f1.div(f2));
例题
- 1.设计一个扑克牌游戏类
花色的设计:
枚举
/**
* 花色
* @author Kygo
*
*/
public enum Suite {
SPADE, HEART, CLUB, DIAMOND, TRUMP;
}
一张牌类
/**
* 一张牌
* @author Kygo
*
*/
public class Card {
// 枚举
private Suite suite;
private int face;
public Card(Suite suite, int face) {
this.suite = suite;
this.face = face;
}
@Override
public String toString() {
String str = "";
switch (suite) {
case SPADE: str = "♠"; break;
case HEART: str = "❤"; break;
case CLUB: str = "♣"; break;
case DIAMOND: str = "♦"; break;
case TRUMP: str = ""; break;
}
switch (face) {
case 1: str += "A"; break;
case 11: str += "J"; break;
case 12: str += "Q"; break;
case 13: str += "K"; break;
case 15: str += "小王"; break;
case 16: str += "大王"; break;
default: str += face;
}
return str;
}
}
一副牌类:
/**
* 扑克
* @author Kygo
*
*/
public class Poker {
private Card[] cardsArray = new Card[54];
private int currentIndex;
/**
* 构造器 : 创建一副新牌
*/
public Poker() {
Suite[] suites = {Suite.SPADE, Suite.HEART, Suite.CLUB, Suite.DIAMOND};
/* int[] faces = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13};
for (int i = 0; i < 52; i++) {
cardsArray[i] = new Card(suites[i / 13], faces[i % 13]);
}*/
for (int i = 0; i < suites.length; i++) {
for (int j = 0; j < 13; j++) {
Card card = new Card(suites[i], j + 1);
cardsArray[i*13 + j] = card;
}
}
cardsArray[52] = new Card(Suite.TRUMP, 15);
cardsArray[53] = new Card(Suite.TRUMP, 16);
}
/**
* 洗牌 : 随机乱序
*/
public void shuffle() {
for (int i = 0, len = cardsArray.length; i < len; i++) {
int randomIndex = (int) (Math.random() * len);
Card temp = cardsArray[i];
cardsArray[i] = cardsArray[randomIndex];
cardsArray[randomIndex] = temp;
}
currentIndex = 0;
}
/**
* 发牌
* @return 一张牌
*/
public Card deal() {
return cardsArray[currentIndex++];
}
/**
* 判断还有没有牌可以发出
* @return 还有牌返回true 否则返回false
*/
public boolean hasMoreCards() {
return currentIndex < cardsArray.length;
}
}
测试类:
public static void display(Player player) {
System.out.print(player.getName() + ":");
for (Card card : player.showCards()) {
System.out.print(card);
}
System.out.println();
}
public static void main(String[] args) {
Player[] playersArray = {
new Player("张三"),
new Player("李四"),
new Player("王五"),
new Player("小白")
};
Poker poker = new Poker();
poker.shuffle();
for (int round = 1; round <= 3; round++) {
for (Player player : playersArray) {
player.getOneCard(poker.deal());
}
}
// 显示每个玩家手上的牌
for (Player player : playersArray) {
display(player);
}
}
- 2.猜数字机器人游戏设计
猜数字机器人类:
/**
* 猜数字机器人
* @author Kygo
*
*/
public class Robot {
private int answer;
private String hint;
private int counter;
/**
* 构造器
*/
public Robot() {
this.reset();
}
/**
* 判断有没有猜中数字
* @param thyAnswer 玩家猜的数字
* @return 如果玩家猜中了数字返回true否则返回false
*/
public boolean judge(int thyAnswer) {
counter += 1;
if (thyAnswer == answer) {
hint = "恭喜你,猜对了!";
return true;
}
else if (thyAnswer > answer) {
hint = "小一点";
}
else {
hint = "大一点";
}
return false;
}
/**
* 重置(重新出随机数,计算器清零，提示信息清空)
*/
public void reset() {
answer = (int) (Math.random() * 100 + 1);
counter = 0;
hint = "";
}
/**
* 获取给用户的提示
* @return 提示字符串
*/
public String getHint() {
return hint;
}
/**
* 获取用户猜的次数
* @return 次数
*/
public int getCounter() {
return counter;
}
}
玩家类:
/**
* 玩家
* @author Kygo
*
*/
public class Player {
private String name;
private Card[] cardsOnHand;
private int totalCards;
/**
* 构造器
* @param name 玩家姓名
*/
public Player(String name) {
this.name = name;
cardsOnHand = new Card[3];
}
/**
* 摸一张牌
* @param card 一张牌
*/
public void getOneCard(Card card) {
if (totalCards < cardsOnHand.length) {
cardsOnHand[totalCards++] = card;
}
}
/**
* 亮牌
* @return 玩家手上所有牌的数组
*/
public Card[] showCards() {
return cardsOnHand;
}
/**
* 获得玩家的姓名
* @return 玩家姓名
*/
public String getName() {
return name;
}
}
测试类:
Robot robot = new Robot();
Scanner input = new Scanner(System.in);
boolean isCorrect = false;
do {
System.out.print("请输入你猜的数字: ");
int thyAnswer = input.nextInt();
isCorrect = robot.judge(thyAnswer);
System.out.println(robot.getHint());
} while (!isCorrect);
if (robot.getCounter() > 7) {
System.out.println("你的智商余额明显不足!");
}
input.close();
作业
- **1.Craps赌博游戏 - 面向对象 **
**两颗色子 - **
第一次:
玩家摇出 7 和11 玩家胜 2 3 或12 庄家胜 其他点数 游戏继续
玩家再摇
如果摇出7点 庄家胜 如果摇出了第一次的点数 玩家胜 其他情况 游戏继续
骰子类:
public class Dice {
private int face;
public Dice() {
this.rollDice();
}
public int rollDice() {
return face = (int) (Math.random() * 6 + 1);
}
public String display() {
return "摇出了" + face + "点.";
}
}
玩家类:
public class Dice {
private int face;
public Dice() {
this.rollDice();
}
public int rollDice() {
return face = (int) (Math.random() * 6 + 1);
}
public String display() {
return "摇出了" + face + "点.";
}
}
游戏类:
public class CrapsGame {
private String hint;
private boolean needsGoOn;
private int fistPoint;
private int currentPoint;
private Player p;
private int bet;
public CrapsGame(Player p) {
this.p = p;
hint = "";
}
public void game(int bet) {
this.bet = bet;
if (bet >= 0 && bet <= p.getMoney()) {
fistPoint = p.rollDices();
System.out.println(p.display());
switch (fistPoint) {
case 7:
case 11:
p.setMoney(p.getMoney() + bet);
hint = "玩家: " + p.getName() + "获胜!";
needsGoOn = false;
break;
case 2:
case 3:
case 12:
p.setMoney(p.getMoney() - bet);
hint = "庄家获胜!";
needsGoOn = false;
break;
default:
needsGoOn = true;
gameGoOn();
break;
}
}
else {
hint = "你没有那么多钱";
}
}
public void gameGoOn() {
while (needsGoOn) {
currentPoint = p.rollDices();
System.out.println(p.display());
if (currentPoint == 7) {
p.setMoney(p.getMoney() - bet);
hint = "庄家获胜!";
needsGoOn = false;
} else if (currentPoint == fistPoint) {
p.setMoney(p.getMoney() + bet);
hint = "玩家: " + p.getName() + "获胜!";
needsGoOn = false;
}
}
}
public String getHint() {
return hint;
}
public boolean isNeedsGoOn() {
return needsGoOn;
}
}
测试类:
/* Dice dice = new Dice();
System.out.println(dice.display());*/
Player p = new Player("张三", 1000);
CrapsGame crapsGame = new CrapsGame(p);
Scanner input = new Scanner(System.in);
do {
System.out.println(p.showMoney());
System.out.print("请下注:");
int bet = input.nextInt();
crapsGame.game(bet);
System.out.println(crapsGame.getHint());
} while (p.getMoney() > 0);
System.out.println(p.showMoney());
System.out.println("游戏结束.");
input.close();
- 2.自动售货机 - 面向对象
商品类:
public class Goods {
private String name;
private int price;
private int count;
public Goods(String name, int price, int count) {
this.name = name;
this.price = price;
this.count = count;
}
public String showGoods() {
return "商品名称: " + name + " 商品价格: " + price + "元"
+" 商品数量: " + count;
}
public int getPrice() {
return price;
}
public String getName() {
return name;
}
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
}
人类:
public class Person {
private String name;
private int money;
private String buyGoods;
public Person(String name, int money) {
this.name = name;
this.money = money;
}
public void shopping(Goods goods) {
if (money > goods.getPrice()) {
money -= goods.getPrice();
goods.setCount(goods.getCount() - 1);
System.out.printf("%s花费%d元购买了%s，还剩%d元\n", name, goods.getPrice(),
goods.getName(), money);
}
else {
System.out.println("钱不够.");
}
}
public int getMoney() {
return money;
}
public void setMoney(int money) {
this.money = money;
}
public String getName() {
return name;
}
public String getBuyGoods() {
return buyGoods;
}
public void setBuyGoods(String buyGoods) {
this.buyGoods = buyGoods;
}
}
售货机类:
public class VendingMachine {
private Goods[] goods;
private String goodsInfo;
private int goodsIndex;
public VendingMachine(Goods[] goods) {
this.goods = goods;
this.goodsInfo = "";
}
public void sell(Person p) {
for (int i = 0; i < goods.length; i++) {
if (p.getBuyGoods().equals(goods[i].getName())) {
goodsIndex = i;
}
}
p.shopping(goods[goodsIndex]);
}
public String show() {
String gi = "";
for (Goods g : goods) {
gi += g.showGoods() + "\n";
}
goodsInfo = gi;
return goodsInfo;
}
}
测试类:
Goods goods1 = new Goods("可乐", 3, 10);
Goods goods2 = new Goods("雪碧", 3, 10);
Goods goods3 = new Goods("啤酒", 3, 10);
Person person = new Person("张三", 100);
VendingMachine vm = new VendingMachine(new Goods[]{goods1, goods2, goods3});
System.out.println("本自动售货机出售以下物品: ");
System.out.println(vm.show());
Scanner input = new Scanner(System.in);
System.out.println("请输入你想买的商品: ");
String wantBuy = input.nextLine();
person.setBuyGoods(wantBuy);
vm.sell(person);
System.out.println(vm.show());
input.close();