Java 类、属性、方法、this 案例
案例 1
编写类A01,定义方法max,实现求某个double数组的最大值,并返回
public class Homework01 {
public static void main(String[] args) {
//编写类A01,定义方法max,实现求某个double数组的最大值,并返回
A01 a01 = new A01();
Double arr[] = {1.0, 4.7, 1.8};
Double res = a01.max(arr);
if (res != null){
System.out.println("arr数组的最大值 " + a01.max(arr));
} else {
System.out.println("arr的输入有误");
}
}
}
class A01 {
public Double max(Double[] arr) {
if (arr.length > 0) {
double max = arr[0];
for (int i = 0; i < arr.length; i++) {
if (max < arr[i]) {
max = arr[i];
}
}
return max;
}
return null;
}
}
案例 2
编写类A02,定义方法find,实现查找某字符串是否在字符串数组中,并返回索引如果找不到,返回-1
public class Homework02 {
public static void main(String[] args) {
//编写类A02,定义方法find,实现查找某字符串是否在字符串数组中,并返回索引如果找不到,返回-1
//1.类名:A02
//2.方法名 find
//3.返回值:int
//4.形参:String String[]
String[] strs = null;
A02 a02 = new A02();
int index = a02.find("jack", strs);
System.out.println("查找的index=" + index);
}
}
class A02 {
public int find(String findStr, String[] strs) {
if (strs != null && strs.length > 0) {
for (int i = 0; i < strs.length; i++) {
if (findStr.equals(strs[i])) {
return i;
}
}
}
return -1;
}
}
案例 3
编写类Book,定义方法updatePrice,实现更改某本书的价格,具体:如果价格>150,则更改为150,如果价格>100,更改为100,否则不变
public class HomeworkO3 {
//编写类Book,定义方法updatePrice,实现更改某本书的价格,
// 具体:如果价格>150,则更改为150,如果价格>100,更改为100,否则不变
//分析:
//1.类名:Book
//2.属性:name,price
//3.方法名:updatePrice
//4.形参:()
//5.返回值:void
//6.提供一个构造器
public static void main(String[] args) {
Book book = new Book("笑傲江湖", 178);
book.info();
book.updatePrice();
book.info();
}
}
class Book{
String name;
double price;
public Book() {
}
public Book(String name, double price) {
this.name = name;
this.price = price;
}
public void updatePrice(){
if (price>150){
price=150;
}else if (price>100){
price=100;
}
}
public void info(){
System.out.println("书名= "+name+"价格="+price);
}
}
案例 4
编写类AO3,实现数组的复制功能copyArr,输入旧数组,返回一个新数组,元素和旧数组一样 Homework04.java
public class Homework04 {
public static void main(String[] args) {
int oldArr[] ={10,20,30};
A03 a03 = new A03();
int newArr[] = a03.copyArr(oldArr);
System.out.println("=========返回的newArr元素情况===========");
for (int i = 0; i < newArr.length ; i++) {
System.out.print(newArr[i]+" ");
}
}
}
class A03 {
public int[] copyArr(int oldArr[]) {
int newArr[] =new int[oldArr.length];
for (int i = 0; i < oldArr.length; i++) {
newArr[i] = oldArr[i];
}
return newArr;
}
}
案例 5
定义一个圆类Circle,定义属性:半径,提供显示圆周长功能的方法,提供显示圆面积的方法 HomeworkO5.java
public class HomeWork05 {
public static void main(String[] args) {
//定义一个圆类Circle,定义属性:半径,提供显示圆周长功能的方法,提供显示圆面积的方法
Circle circle = new Circle(3);
System.out.println("周长="+circle.len());
System.out.println("面积="+circle.area());
}
}
class Circle {
double radius;
public Circle(double radius) {
this.radius = radius;
}
public double area() {
return Math.PI * radius * radius;
}
public double len() {
return 2 * Math.PI * radius;
}
}
案例 6
编程创建一个Cale计算类,在其中定义2个变量表示两个操作数,定义四个方法实现求和、差、乘、商(要求除数为0的话,要提示)并创建两个对象,分别测试
public class Homework06 {
public static void main(String[] args) {
Cale cale = new Cale(1,5);
System.out.println("和="+cale.sum());
System.out.println("差="+cale.minus());
System.out.println("积="+cale.mul());
Double divRes = cale.div();
if(divRes != null){
System.out.println("除="+cale.div());
}
}
}
class Cale {
double num1;
double num2;
public Cale(double num1, double num2) {
this.num1 = num1;
this.num2 = num2;
}
public double sum() {
return num1 + num2;
}
public double minus() {
return num1 - num2;
}
public double mul() {
return num1 * num2;
}
public Double div() {
if (num2 == 0) {
System.out.println("num2不能为0");
return null;
} else {
return num1 / num2;
}
}
}
案例 7
定义Music类,里面有音乐名name、音乐时长times属性,并有播放play功能和返回本身属性信息的功能方法getlnfo
Homework07.java
public class Homework07 {
public static void main(String[] args) {
Music music = new Music("笑傲江湖", 300);
music.play();
System.out.println(music.getInfo());
}
}
class Music {
String name;
int times;
public Music(String name, int times) {
this.name = name;
this.times = times;
}
public void play() {
System.out.println("音乐 " + name + "正在播放中......");
}
public String getInfo() {
return "音乐 " + name + "播放时长为 " + times;
}
}
案例 8
创建一个Employee类,属性有((名字,性别,年龄,职位,薪水),提供3个构造方法,可以初始化
(1)(名字,性别,年龄,职位,薪水)
(2)(名字,性别,年龄)
(3)(职位,薪水)
要求充分复用
构造器
Homework08.java
public class Homework08 {
public static void main(String[] args) {
}
}
class Employee {
String name;
String gender;
String age;
String job;
String sal;
public Employee(String job, String sal) {
this.job = job;
this.sal = sal;
}
public Employee(String name, String gender, String age) {
this.name = name;
this.gender = gender;
this.age = age;
}
public Employee(String name, String gender, String age, String job, String sal) {
this(name, gender, age);
this.job = job;
this.sal = sal;
}
}
案例 9
将对象作为参数传递给方法。Homework09.java
题目要求:
(1)定义一个Circle类,包含一个double型的radius属性代表圆的半径,findArea()方法返回圆的面积。
(2)定义一个类PassObject,在类中定义一个方法printAreas(),该方法的定义如下:
public void printAreas(Circle c, int times)1/方法签名/声明
(3)在printAreas方法中打印输出1到times之间的每个整数半径值,以及对应的面积。例如,times为 5,则输出半径1,2,3,4,5,以及对应的圆面积。
(4)在main方法中调用printAreas()方法,调用完毕后输出当前半径值。程序运行结果如图所示
public class Homework09 {
public static void main(String[] args) {
PassObject po = new PassObject();
po.printAreas(new Circle(),5);
}
}
class Circle {
double radius;
public Circle() {
}
public Circle(double radius) {
this.radius = radius;
}
public double findArea() {
return Math.PI * radius * radius;
}
public void setRadius(double radius) {
this.radius = radius;
}
}
class PassObject {
public void printAreas(Circle c, int times) {
System.out.println("radius\tarea");
for (int i = 1; i <= times; i++) {
c.setRadius(i);
System.out.println((double)i+" \t"+c.findArea());
}
}
}
案例 10
有个人Tom设计他的成员变量.成员方法,可以电脑猜拳,电脑每次都会随机生成0,1,2
0表示石头1表示剪刀2表示布并要可以显示Tom的输赢次数(清单)
public class MoraGame {
public static void main(String[] args) {
//创建一个玩家对象
Tom t = new Tom();
//用来记录最后输赢的次数
int isWinCount = 0;
//创建一个二维数组,用来接收局数,Tom出拳情况以及电脑出拳情况
int[][] arr1 = new int[3][3];
int j = 0;
//创建一个一维数组,用来接收输赢情况
String[] arr2 = new String[3];
Scanner scanner = new Scanner(System.in);
for (int i = 0; i < 3; i++) {
//获取玩家出的拳
System.out.println("请输入你要出的拳(0-拳头,1-剪刀,2-布) :");
int num = scanner.nextInt();
t.setTomGussNum(num);
int tomGuess = t.getTomGuessNum();
arr1[i][j + 1] = tomGuess;
//获取电脑出的拳
int comGuess = t.computerNum();
arr1[i][j + 2] = comGuess;
//将玩家猜的拳头与电脑做比较
String isWin = t.vsComputer();
arr2[i] = isWin;
arr1[i][j] = t.count;
//对每一局情况进行输出
System.out.println("===================================");
System.out.println("局数\t玩家的出拳\t电脑的出拳\t输赢情况");
System.out.println(t.count + " \t" + tomGuess + " \t" + "\t\t" + comGuess + " \t\t\t" + isWin);
System.out.println("===================================");
System.out.println("\n\n");
isWinCount = t.winCount(isWin);
}
//对游戏最终结果进行输出
System.out.println("局数\t玩家的出拳\t电脑的出拳\t输赢情况");
for (int a = 0; a < arr1.length; a++) {
for (int b = 0; b < arr1[a].length; b++) {
System.out.print(arr1[a][b] + "\t\t\t");
}
System.out.println(arr2[a]);
System.out.println();
}
System.out.println("你赢了" + isWinCount + "次");
}
}
class Tom {
//玩家出拳的类型
int tomGuessNum; //0,1, 2
//电脑出拳的类型
int comGuessNum; //0,1, 2
//玩家赢的次数
int winCountNum;
//比赛的次数
int count = 1; //一共比赛3次
public void showInfo() {
//...
}
/**
* 电脑随机生成猜拳的数字的方法
*
* @return
*/
public int computerNum() {
Random r = new Random();
comGuessNum = r.nextInt(3); // 方法 返回0-2的随机数
return comGuessNum;
}
/**
* 设置玩家猜拳的数字的方法
*
* @param tomGuessNum
*/
public void setTomGussNum(int tomGuessNum) {
if (tomGuessNum > 2 || tomGuessNum < 0) {
throw new IllegalArgumentException("数字输入错误");
}
this.tomGuessNum = tomGuessNum;
}
public int getTomGuessNum() {
return tomGuessNum;
}
/**
* 比较猜拳的结果
*
* @return 玩家赢返回true 否则返回false;
*/
public String vsComputer() {
if (tomGuessNum == 0 && comGuessNum == 1) {
return "你赢了";
} else if (tomGuessNum == 1 && comGuessNum == 2) {
return "你赢了";
} else if (tomGuessNum == 2 && comGuessNum == 0) {
return "你赢了";
} else if (tomGuessNum == comGuessNum) {
return "平手";
} else {
return "你输了";
}
}
/**
* 记录玩家赢的次数
*
* @return
*/
public int winCount(String s) {
count++;//控制玩的次数
if (s.equals("你赢了")) { //统计赢的次数
winCountNum++;
}
return winCountNum;
}
}