010面向对象编程（上）-3

封装和隐藏

测试封装

package com.atguigu.exer;

public class PersonTest {
	public static void main(String[] args) {
		Person test = new Person();
		test.setAge(131);
		System.out.println(test.getAge());
//		test.age = 10; //The field Person.age is not visible
	}
}

class Person{
	private int age;
	public void setAge(int i){
		if(i<0 || i>130){
			System.out.println("输入违规");
		}else{
			age = i;
		}
	}
	public int getAge(){
		return age;
	}
}

构造器

测试构造器

package com.atguigu.exer;
/*
 * 3.编写两个类，TriAngle和TriAngleTest，其中TriAngle类中声明私有的底 边长base和高height，
 * 同时声明公共方法访问私有变量。
 * 此外，提供类 必要的构造器。另一个类中使用这些公共方法，计算三角形的面积。
 */
public class TriAngleTest {
	public static void main(String[] args) {
		TriAngle triangle = new TriAngle();		
		double  base = triangle.getBase();
		double height = triangle.getHeight();
		double area = triangle.getArea();
		System.out.println("长：" + base + "，高：" + height + "，面积：" + area);
		
		triangle.setBase(10);
		triangle.setHeight(5);
		System.out.println(triangle.getArea());
	}
}

class TriAngle{
	private double base;
	private double height;
	TriAngle(){
		base = 5;
		height = 5;
	}

	public double getBase(){
		return base;
	}
	public void setBase(double b){
		base = b;
	}
	public double getHeight(){
		return height;
	}
	public void setHeight(double h){
		height = h;
	}
	public double getArea(){
		return height * base / 2;
	}
}

测试构造器重载

package com.atguigu.exer;
/*
 * 定义Student类,有4个属性：  String name; int age;  String school;  String major;
定义Student类的3个构造器:
第一个构造器Student(String n, int a)设置类的name和age属性；
第二个构造器Student(String n, int a, String s)设置类的name, age 和school属性；
第三个构造器Student(String n, int a, String s, String m)
设置类的name, age ,school和major属性；
在main方法中分别调用不同的构造器创建的对象，并输出其属性值。

 */
public class StudentTest {
	public static void main(String[] args) {
		Student student = new Student();
		Student student1 = new Student("tom",18);
		Student student2 = new Student("tom",18,"霍格沃兹");
		Student student3 = new Student("tom",18,"霍格沃兹","麻瓜魔法术");
	}
}

class Student{
	private String name;
	private int age;
	private String school;
	private String major;
	
	Student(){	
	}
	Student(String n, int a){
		name = n;
		age = a;
		System.out.println(name + "\t" + age);
	}
	Student(String n, int a, String s){
		name = n;
		age = a;
		school = s;
		System.out.println(name + "\t" + age + "\t" + school);
	}
	Student(String n, int a, String s, String m){
		name = n;
		age = a;
		school = s;
		major = m;
		System.out.println(name + "\t" + age + "\t" + school + "\t" + major);
	}
	
}

this的使用

使用this访问属性和方法时， 如果在本类中未找到，会从父 类中查找

实验1：Account_Customer

package com.atguigu.java;
/*
 * 1、写一个名为 Account 的类模拟账户。该类的属性和方法如下图所示。该类包括的属性：
账号 id，余额 balance，年利率 annualInterestRate；包含的方法：访问器方法（getter 和 setter
方法），取款方法 withdraw()，存款方法 deposit()。
 */
public class Account {
	private int id;
	private double balance;
	private double annualInterestRate;
	
	public Account(){
		this.balance = 10000;
	}
	public Account(int id, double balance, double annualInterestRate ){
		this.id = id;
		this.balance = balance;
		this.annualInterestRate = annualInterestRate;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public double getBalance() {
		return balance;
	}
	public void setBalance(double balance) {
		this.balance = balance;
	}
	public double getAnnualInterestRate() {
		return annualInterestRate;
	}
	public void setAnnualInterestRate(double annualInterestRate) {
		this.annualInterestRate = annualInterestRate;
	}
	
	public void withdraw (double amount){ //取钱
		if(amount<=this.balance && amount>0){
			this.balance -= amount;
			System.out.println("成功取出：" + amount);
		}else{
			System.out.println("余额不足，取款失败");
		}
	}
	public void deposit (double amount){ //存钱
		if(amount>0){
			this.balance += amount;
			System.out.println("成功存入：" + amount);
		}else{
			System.out.println("请存入有效的数字");
		}
	}
}

package com.atguigu.java;
/*
 * a. 声明三个私有对象属性：firstName、lastName 和 account。
b. 声明一个公有构造器，这个构造器带有两个代表对象属性的参数（f 和 l）
c. 声明两个公有存取器来访问该对象属性，方法 getFirstName 和 getLastName 返回相应的属
性。
d. 声明 setAccount 方法来对 account 属性赋值。
e. 声明 getAccount 方法以获取 account 属性。
 */
public class Customer {
	private String firstName;
	private String lastName;
	private Account account;
	
	public Customer(){
		
	}
	public Customer(String f,String l){
		this.firstName = f;
		this.lastName = l;
	}
	
	public String getFirstName() {
		return firstName;
	}
	public String getLastName() {
		return lastName;
	}
	public Account getAccount() {
		return account;
	}
	public void setAccount(Account account){
		this.account = account;
	}
	
}

package com.atguigu.java;
/*
 * （1） 创建一个 Customer ，名字叫 Jane Smith, 他有一个账号为 1000，余额为 2000 元，
年利率为 1.23％ 的账户。
（2） 对 Jane Smith 操作。
存入 100 元，再取出 960 元。再取出 2000 元。
打印出 Jane Smith 的基本信息
 */
public class TestCustomer {
	public static void main(String[] args) {
		Customer customer = new Customer("Smith","Jane");
		Account account = new Account();
		customer.setAccount(account);
		customer.getAccount().setId(1000);
		customer.getAccount().setBalance(2000);
		customer.getAccount().setAnnualInterestRate(1.23);
		
		customer.getAccount().deposit(100);
		customer.getAccount().withdraw(960);
		customer.getAccount().withdraw(2000);
		System.out.println("Customer [" + customer.getFirstName() + ", " + customer.getLastName() +
				"] has a account: id is " + customer.getAccount().getId() + ", " +
				"annualInterestRate is " + customer.getAccount().getAnnualInterestRate() + "%" 
				+ ", " + "balance is " + customer.getAccount().getBalance());
		
	}
}

实验2：Account_Customer_Bank

package com.atguigu.java2;

import javax.swing.plaf.synth.SynthSeparatorUI;

public class Account {
	private double balance;
	
	public Account(){
		
	}
	public Account(double init_balance){  //初始化
		this.balance = init_balance;
	}
	
	public double getBalance(){  //返回余额
		return balance;
	}
	public void deposit(double amt){ //存钱
		if(amt > 0){
			balance += amt;
			System.out.println("成功存款: " + amt);
		}else{
			System.out.println("存款失败");
		}
	}
	public void withdraw(double amt){  //取款
		if(amt > 0 && amt <= balance){  
			balance -= amt;
			System.out.println("成功取款: " + amt); 
		}else{
			System.out.println("取款失败");
		}
	}
}

package com.atguigu.java2;

public class Customer {
	private String firstName;
	private String lastName;
	private Account account;
	
	public Customer(){
		
	}
	public Customer(String f, String l){
		firstName = f;
		lastName = l;
	}
	
	public Account getAccount() {
		return account;
	}
	public void setAccount(Account account) {
		this.account = account;
	}
	public String getFirstName() {
		return firstName;
	}
	public String getLastName() {
		return lastName;
	}
	
}

package com.atguigu.java2;

public class Bank {
	private Customer[] customers;
	private int numberOfCustomer;
	
	public Bank(){
		customers = new Customer[10];
	}
	
	public void addCustomer(String f, String l){
		Customer cust = new Customer(f, l);
		customers[numberOfCustomer++] = cust;
	}
	public int getNumberOfCustomer(){
		return numberOfCustomer;
	}
	public Customer getCustomer(int index){
		return customers[index];
	}	
}

package com.atguigu.java2;

import java.util.Scanner;

public class BankTest {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		Bank bank = new Bank();
		
		for(int i = 0; i < 10; i++){
            System.out.print("请输入名字：" + "\n");
            String firstName = scanner.next();
            System.out.print("请输入姓氏：" + "\n");
            String lastName = scanner.next();
            bank.addCustomer(firstName, lastName);

            bank.getCustomer(i).setAccount(new Account(2000));
            bank.getCustomer(i).getAccount().deposit(200);
            bank.getCustomer(i).getAccount().withdraw(1000);
            System.out.println("当前客户为: [" + bank.getCustomer(i).getFirstName() + ", " + bank.getCustomer(i).getLastName() + "], 余额为: " + bank.getCustomer(i).getAccount().getBalance());
            System.out.println("当前客户数量: " + (i + 1));
            System.out.println();
		}
		
		System.out.println("****************************");
		System.out.println("当前客户数量为: " + bank.getNumberOfCustomer());
	}
}

package和import的使用

练习1：内存调用

package com.atguigu.exer1;
class Value{
    int i = 15;
}
public class Test{
	public static void main(String argv[]) {
		Test t = new Test();
		t.first();
	}
	
	public void first() {
		int i = 5;
		Value v = new Value();
		v.i = 25;
		second(v, i);
		System.out.println(v.i);
	}
	
	public void second(Value v, int i) {
		i = 0;
		v.i = 20;
		Value val = new Value();
		v = val;
		System.out.print(v.i + " " + i);
	}
}

练习2：运行结果

package com.atguigu.exer1;

class Test {
	public static void main(String[] args) {
		int i = 0;
		change(i);
		i = i++;
		System.out.println("i = " + i);
	}
	public static void change(int i){
		i++;
	}
}

package com.atguigu.exer1;

class Test {
	public static void main(String[] args) {
		String str = new String("world");
		char[] ch = new char[]{'h','e','l','l','o'};
		change(str,ch);
		System.out.println(str);
		System.out.println(String.valueOf(ch));
	}
	public static void change(String str, char[] arr){
		str = "change";
		arr[0] = 'a';
		arr[1] = 'b';
		arr[2] = 'c';
		arr[3] = 'd';
		arr[4] = 'e';
	}
}

package com.atguigu.exer1;

class Circle {
	private double radius;

	public Circle(double r) {
		radius = r;
	}

	public Circle compare(Circle cir) {
		return (this.radius>cir.radius)?this: cir;
	}
}

public class Test {
	public static void main(String[] args) {
		Circle cir1 = new Circle(1.0);
		Circle cir2 = new Circle(2.0);
		Circle cir;
		cir = cir1.compare(cir2);
		if (cir1 == cir)
			System.out.println("圆1的半径比较大");
		else
			System.out.println("圆2的半径比较大");
	}
}