Java面向对象编程(中级)
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面向对象编程(中级)
包
访问修饰符
封装
01:
public class Encapsulation01
{
public static void main(String[] args)
{
Person person = new Person();
person.name = "Tom";
person.setAge(30);
person.setSalary(30000);
}
}
class Person
{
public String name;
private int age;
private double salary;
public void setSalary(double salary)
{
this.salary = salary;
}
public double getSalary()
{
return this.salary;
}
public void setAge(int age)
{
if (age >= 1 && age <= 123)
this.age = age;
else
{
System.out.println("Input Error");
this.age = 18;//给个默认age
}
}
public int getAge()
{
return this.age;
}
public void setName(String name)
{
if (name.length() >= 2 && name.length() <= 6)
this.name = name;
else
{
System.out.println("Input Error");
this.name = "wuming";
}
}
public String getName()
{
return this.name;
}
public String printElem()
{
return "name = "+name+" age = "+age+" salary = "+salary;
}
}
01:
public class Encapsulation01
{
public static void main(String[] args)
{
Person person = new Person();
person.name = "Tom";
person.setAge(30);
person.setSalary(30000);
}
}
class Person
{
public String name;
private int age;
private double salary;
public Person(){}
public Person(String name,int age,double salary){
//this.name = name;
// this.age = age;
// this.salary = salary;
setName(name);
setAge(age);
setSalary(salary);
}
public void setSalary(double salary)
{
this.salary = salary;
}
public double getSalary()
{
return this.salary;
}
public void setAge(int age)
{
if (age >= 1 && age <= 123)
this.age = name;
else
{
System.out.println("Input Error");
this.age = 18;//给个默认age
}
}
public int getAge()
{
return this.age;
}
public void setName(String name)
{
if (name.length() >= 2 && name.length() <= 6)
this.name = name;
else
{
System.out.println("Input Error");
this.name = "wuming";
}
}
public String getName()
{
return this.name;
}
public String printElem()
{
return "name = "+name+" age = "+age+" salary = "+salary;
}
}
小练习
package HelloDemo;
public class Account {
private String name;
private double balance;
private String password;
public Account(){}
public Account(String name, double balance, String password) {
this.setBalance(balance);
this.setName(name);
this.setPassword(password);
}
public String getName() {
return name;
}
public void setName(String name) {
if(name.length() >= 2 && name.length() <= 4)
this.name = name;
else
{
System.out.println("Input Error");
this.name = "wuming";
}
}
public double getBalance() {
return balance;
}
public void setBalance(double balance) {
if (balance > 20)
this.balance = balance;
else {
System.out.println("Input Error,balance = 0");
}
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
if (password.length()==6)
this.password = password;
else
{
System.out.println("Input Error password = 000000");
this.password = "000000";
}
}
public void showInfo()
{
//可以增加权限的校验
System.out.println("name = "+name+" balance = "+balance+" password = "+password);
}
}
//-------------------------------------------------------------------------------
package HelloDemo;
public class TestAccount {
public static void main(String[] args)
{
Account account = new Account();
account.setName("Tom");
account.setBalance(60);
account.setPassword("123456");
account.showInfo();
}
}
继承
01：
package JiCWorkDemo;
public class Pupil {
public String name;
public int age;
private double score;
public void setScore(double score) {
this.score = score;
}
public void testing()
{
System.out.println("pupil name= "+name);
}
public void showInfo()
{
System.out.println("name = "+name+" age = "+age+" score = "+score);
}
}
//===========================================
package JiCWorkDemo;
public class Graduate extends Pupil{
public void testing()
{
System.out.println("Graduate name= "+name);
}
}
//===========================================
package JiCWorkDemo;
public class WorkDemo {
public static void main(String[] args)
{
Pupil pupil = new Pupil();
pupil.name = "Tom";
pupil.age = 11;
pupil.testing();
pupil.setScore(50);
pupil.showInfo();
System.out.println("========");
Graduate graduate = new Graduate();
graduate.name = "Jack";
graduate.age = 23;
graduate.testing();
graduate.setScore(80);
graduate.showInfo();
}
}
继承的深入讨论/细节问题
01:
package JiCWorkDemo;
public class Base {
public int n1 = 100;
protected int n2 = 200;
int n3 = 300;
private int n4 = 400;
public int getN4()
{
return n4;
}
public void callTest400()
{
test400();
}
public Base()
{
System.out.println("Base()......");
}
public void test100()
{
System.out.println("test100");
}
protected void test200()
{
System.out.println("test200");
}
void test300()
{
System.out.println("test300");
}
private void test400()
{
System.out.println("test400");
}
}
//==============================================
package JiCWorkDemo;
public class Son extends Base{
public Son()
{
System.out.println("sub()...");
}
public void say0k()
{
System.out.println(n1+n2+n3);
test100();
test200();
test300();
//System.out.println(n4);//Error
//test400();//Error
System.out.println("n4 = "+getN4());
callTest400();
}
}
继承的本质分析
如果查找过程中，父类的age是private，而爷爷类的age是public，但还是会报错，因为找到父类的age是private以后就会报错，不会去找爷爷类的age
小练习
结果如下:
我是A类
hahah我是B类的有参构造
我是c类的有参构造
我是c类的无参构造
01:
package ExerciseDemoWork;
public class Computer {
private String cpu;
private int memory;
private int disk;
public Computer(String cpu, int memory, int disk) {
this.cpu = cpu;
this.memory = memory;
this.disk = disk;
}
public String getDetails()
{
return "cpu = "+cpu+" memory = "+memory+" disk = "+disk;
}
public String getCpu() {
return cpu;
}
public void setCpu(String cpu) {
this.cpu = cpu;
}
public int getMemory() {
return memory;
}
public void setMemory(int memory) {
this.memory = memory;
}
public int getDisk() {
return disk;
}
public void setDisk(int disk) {
this.disk = disk;
}
}
//============================================================================
package ExerciseDemoWork;
public class PC extends Computer{
private String brand;
public PC(String cpu, int memory, int disk, String brand) {
super(cpu, memory, disk);
this.brand = brand;
}
public String getBrand() {
return brand;
}
public void Scala核心编程_第08章 面向对象编程(中级补充)--java动态绑定与静态绑定