Java学习笔记 - 第007天
2016-12-06 本文已影响0人
迷茫o
每日要点
二维数组
int a[][] = new int[2][3];
二维数组 a 可以看成一个两行三列的数组。
- 例子1:学生的成绩
int[][] scores = new int[5][3];
for (int i = 0; i < scores.length; i++) {
for (int j = 0; j < scores[i].length; j++) {
scores[i][j] = (int) (Math.random() * 101);
}
}
- 例子2:杨辉三角:
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
int[][] y = new int[10][];
for (int i = 0; i < y.length; i++) {
y[i] = new int[i + 1];
for (int j = 0; j < y[i].length; j++) {
if (j == 0 || j == i) {
y[i][j] = 1;
}
else {
y[i][j] = y[i - 1][j] + y[i - 1][j - 1];
}
System.out.print(y[i][j] + "\t");
}
System.out.println();
}
面向对象
对象是可以接收消息的实体
特征 :
1.一切都是对象
2.对象都有属性和行为
3.每个对象都是独一无二的
4.对象都属于某个类
类是对象的蓝图和模板
- 数据抽象 - 属性
- 构造器 - 创建对象需要使用构造器
- 行为抽象 - 方法
面向对象编程的第1步 - 定义类
public class Student {
// 数据抽象 - 属性 - 找名称
private String name;
private int age;
// 构造器
public Student(String n, int a) {
name = n;
age = a;
}
// 行为抽象 - 方法 - 找动词
public void play(String gameName) {
System.out.println(name + "正在玩" + gameName + ".");
}
public void study() {
System.out.println(name + "正在学习.");
}
public void watchJapaneseAV() {
if (age >= 18) {
System.out.println(name + "正在观看岛国爱情动作片.");
}
else {
System.out.println(name + "只能观看《熊出没》.");
}
}
}
**面向对象编程第2步 - 创建对象 **
// new 构造器();
Student stu = new Student("王大锤", 15);
面向对象编程第3步 - 给对象发消息
stu.study();
stu.play("LOL");
stu.watchJapaneseAV();
Student stu2 = new Student("张三", 18);
stu2.study();
stu2.play("斗地主");
stu2.watchJapaneseAV();
this 关键字
this 代表这个对象
- 例子:
public class Dog {
private String nickname;
private boolean isLarge;
public Dog(String nickname, boolean isLarge) {
// this 代表这个对象
this.nickname = nickname;
this.isLarge = isLarge;
}
public void bark() {
System.out.println(nickname + ": 汪汪汪....");
}
public void keepTheDoor() {
if (isLarge) {
System.out.println(nickname + "正在看门.");
}
else {
System.out.println(nickname + "不能看门.");
}
}
}
主函数:
Dog dog1 = new Dog("旺财", true);
dog1.bark();
dog1.keepTheDoor();
Dog dog2 = new Dog("花花", false);
dog2.bark();
dog2.keepTheDoor();
其他内容
写代码的终极原则: 高内聚 低耦合
high cohesion low coupling
1TBS - One True Bracing Style 打{}风格
Allman - FreeBSD
如果定义类时没有写任何一个构造器
那么系统会自动添加一个默认的隐式构造器(平庸构造器)
public Clock() {
}
写代码低耦合 举例:
System.out.printf("%02d:%02d:%02d\n", hour, minute, second);
这样写代码就跟控制台紧紧耦合在了一起 ,应该这样写:
return String.format("%02d:%02d:%02d", hour, minute, second);
窗口类
JFrame
// 创建窗口对象
JFrame f = new JFrame("我的第一个窗口");
// 通过给窗口对象发消息来设置和显示窗口
f.setSize(400, 300); // 大小
f.setLocationRelativeTo(null); // 窗口摆放
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //关窗口自动关闭程序
Clock clock = new Clock();
JLabel label = new JLabel(clock.display()); // 创建标签
label.setHorizontalAlignment(JLabel.CENTER); // 设置水平对齐 - 居中
Font font = new Font("微软雅黑", Font.BOLD, 36); // 设置字体
label.setFont(font); // 将字体添加到标签
f.add(label); // 将标签添加到窗口
new Timer(1000, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
clock.run();
label.setText(clock.display());
}
}).start();
f.setVisible(true); // 显示窗口
昨天作业讲解
- 1.买彩票红色球 1~33 蓝色球 1~16
01 05 11 17 18 22 05
08 10 22 23 31 32 11
数字不能重复
输入 几 随机选出 几组号码
Scanner input = new Scanner(System.in);
System.out.print("机选几注: ");
int n =input.nextInt();
input.close();
for (int counter = 1; counter <= n; counter++) {
int[] redBalls = new int[6];
for (int i = 0; i < redBalls.length;) {
// 生成1~33的随机数作为红色球的号码
int number = (int) (Math.random() * 33 + 1);
// 检查此号码在之前选中的号码中有没有出现过
boolean isDuplicated = false;
for (int j = 0; j < i; j++) {
if (redBalls[j] == number) {
isDuplicated = true;
break;
}
}
if (!isDuplicated) {
redBalls[i] = number;
i += 1;
}
}
bubbleSort(redBalls);
for (int x : redBalls) {
System.out.printf("%02d ", x);
}
int blueBall = (int) (Math.random() * 16 + 1);
System.out.printf("| %02d\n", blueBall);
}
}
public static void bubbleSort(int[] array) {
// 数组有N个数，需要N-1次循环
boolean swapped =true;
for (int i = 1; swapped && i < array.length; i++) {
swapped = false;
for (int j = 0;j < array.length - i; j++) {
if (array[j] > array[j + 1]) {
int temp = array[j];
array[j] = array[j + 1];
array[j + 1] = temp;
swapped = true;
}
}
}
}
例子
-
1.电子钟
电子钟类:
public class Clock {
private int hour;
private int minute;
private int second;
// 如果定义类时没有写任何一个构造器
// 那么系统会自动添加一个默认的隐式构造器(平庸构造器)
// public Clock() {
// }
public Clock() {
// 拿系统时间
// Java 7-
// Calendar cal = new GregorianCalendar();
// this.hour = cal.get(Calendar.HOUR_OF_DAY);
// this.minute = cal.get(Calendar.MINUTE);
// this.second = cal.get(Calendar.SECOND);
// Java 8+
LocalDateTime time = LocalDateTime.now();
this.hour = time.getHour();
this.minute = time.getMinute();
this.second = time.getSecond();
}
public Clock(int hour, int minute, int second) {
this.hour = hour;
this.minute = minute;
this.second = second;
}
public String display() {
// 这样写代码就跟控制台紧紧耦合在了一起
// System.out.printf("%02d:%02d:%02d\n", hour, minute, second);
return String.format("%02d:%02d:%02d", hour, minute, second);
}
public void run() {
second += 1;
if (second == 60) {
second = 0;
minute += 1;
if (minute == 60) {
minute = 0;
hour += 1;
if (hour == 24) {
hour = 0;
}
}
}
}
}
主函数:
Clock clock = new Clock();
System.out.println(clock.display());
while (true) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
clock.run();
System.out.println(clock.display());
}
作业
- 1.定义一个类 描述手机 品牌尺寸等 打电话 发短信等
call send short message install application App
uninstall / remove update
手机类:
public class MobilePhone {
private String brand;
private double size;
private double price;
private String phoneModel;
private String manufacturer;
private String number;
public MobilePhone(String brand, double size, double price, String phoneModel,
String manufacturer, String number) {
this.brand = brand;
this.size = size;
this.price = price;
this.phoneModel = phoneModel;
this.manufacturer = manufacturer;
this.number = number;
}
public String displayInformation() {
return String.format("手机信息: \n品牌: " + brand + "\n型号: " + phoneModel
+ "\n制造商: " + manufacturer + "\n尺寸: %.2f寸 \n价格: %.2f元 \n电话号码: "
+ number, size,price);
}
public String call(String number) {
return String.format(this.number + " 正在给 " + number + "打电话");
}
public String sendShortMessage(String number) {
return String.format(this.number + " 正在给 " + number + "发短信");
}
public String installAPP(String app) {
return String.format(this.phoneModel + " 正在安装 " + app);
}
public String uninstallAPP(String app) {
return String.format(this.phoneModel + " 正在卸载 " + app);
}
public String updateAPP(String app) {
return String.format(this.phoneModel + " 正在更新 " + app);
}
}
主函数:
MobilePhone mobilePhone = new MobilePhone("魅族", 5.5, 2000, "魅蓝Note",
"中国", "18908042994");
System.out.println(mobilePhone.displayInformation());
System.out.println(mobilePhone.call("18602132435"));
System.out.println(mobilePhone.sendShortMessage("18602132435"));
System.out.println(mobilePhone.installAPP("熊猫TV"));
System.out.println(mobilePhone.uninstallAPP("UC浏览器"));
System.out.println(mobilePhone.updateAPP("QQ"));
-
2.写个程序 模拟 奥特曼打小怪兽
hp mp
攻击行为
攻击参数 小怪兽
奥特曼必杀技
小怪兽反击
奥特曼类:
public class Ultraman {
private String name;
int hp;
int mp;
public Ultraman(String name, int hp, int mp) {
this.name = name;
this.hp = hp;
this.mp = mp;
}
public void attack(Monster m) {
m.hp -= 20;
System.out.println(this.getName() + "普通攻击了" +
m.getName());
}
public void hugeAttack(Monster m) {
m.hp -= 50;
System.out.println(this.getName() + "暴击了" +
m.getName());
}
public void magicalAttack(Monster[] mArray) {
for (Monster m : mArray) {
m.hp -= 20;
}
this.mp -= 100;
System.out.println(this.getName() + "发动大招攻击了所有小怪兽");
}
public void status() {
System.out.printf(this.getName() + " hp:%d mp:%d\n", hp, mp);
}
public String getName() {
return this.name;
}
}
小怪兽类:
public class Monster {
private String name;
int hp;
public Monster(String name, int hp) {
this.name = name;
this.hp = hp;
}
public void attackBack(Ultraman u) {
u.hp -= 10;
System.out.println(this.getName() + "反击了" + u.getName());
}
public String getName() {
return this.name;
}
public void status() {
System.out.printf(this.getName() + "小怪兽 hp:%d\n", hp);
}
}
主函数:
Ultraman ultraman = new Ultraman("迪迦奥特曼", 500, 200);
Monster[] monsters = new Monster[3];
for (int i = 0; i < monsters.length; i++) {
monsters[i] = new Monster("小怪兽" + (i + 1) + "号", 100);
}
Scanner input = new Scanner(System.in);
while (ultraman.hp > 0) {
System.out.printf(ultraman.getName() + "，请选择攻击方式: \n" + "1.普通攻击 2.发动暴击 3.魔法攻击\n");
int attackModel = input.nextInt();
System.out.print(ultraman.getName() + "，请选择攻击哪个小怪兽: ");
int monsterNum = input.nextInt();
if (monsters[monsterNum - 1].hp > 0) {
switch (attackModel) {
case 1:
ultraman.attack(monsters[monsterNum - 1]);
monsters[monsterNum - 1].attackBack(ultraman);
ultraman.status();
monsters[monsterNum - 1].status();
break;
case 2:
ultraman.hugeAttack(monsters[monsterNum - 1]);
monsters[monsterNum - 1].attackBack(ultraman);
ultraman.status();
monsters[monsterNum - 1].status();
break;
case 3:
ultraman.magicalAttack(monsters);
for (int i = 0; i < monsters.length; i++) {
monsters[i].attackBack(ultraman);
}
ultraman.status();
for (int i = 0; i < monsters.length; i++) {
monsters[i].status();
}
break;
}
}
else {
System.out.println(monsters[monsterNum - 1].getName() + "没有hp了，已经死亡");
}
}
input.close();
-
3.改造成面向对象 围墙 过道 fencePrice aislePrice
过道类:
public class Aisle {
private static final double AISLE_UNIT_PRICE = 38.5;
private double radius;
public Aisle(double radius) {
this.radius = radius;
}
public double area() {
return Math.PI * this.radius * this.radius;
}
public double area(double radius) {
return Math.PI * radius * radius;
}
public double aislePrice(double r) {
return (this.area() - area(r))* AISLE_UNIT_PRICE;
}
}
围墙类:
public class Fence {
private static final double FENCE_UNIT_PRICE = 15.5;
private double radius;
public Fence(double radius) {
this.radius = radius;
}
public double perimeter() {
return 2 * Math.PI * this.radius;
}
public double fencePrice() {
return this.perimeter() * FENCE_UNIT_PRICE;
}
}
主函数:
Scanner input = new Scanner(System.in);
System.out.print("请输入游泳池的半径: ");
double r = input.nextDouble();
if (r > 0) {
Fence fence = new Fence(r + 3);
System.out.printf("围墙的造价为: %.2f元\n", fence.fencePrice());
Aisle aisle = new Aisle(r + 3);
System.out.printf("过道的造价: %.2f元", aisle.aislePrice(r));
}
else {
System.out.println("游泳池的半径应该是一个正数.");
}
input.close();
