Java 入门21 java 进阶大纲 及复习

 

 

回顾类 对象  构造器 ArrayList的基本使用

Animal类

package com.renzen.Animal.Day1;

public class Animal {
    private String name;
    private String sex;

    //有参构造器

    public Animal(String name, String sex) {
        this.name = name;
        this.sex = sex;
    }


    //无参构造器

    public Animal() {
    }

    //get set

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
}

Test

package com.renzen.Animal.Day1;

import java.util.ArrayList;

public class Test {
    public static void main(String[] args) {
        //创建动物类ArrayList 集合
        ArrayList<Animal> list=new ArrayList<>();

        //创建Animal实例
        Animal animal=new Animal("金毛","公");
        Animal animal1=new Animal("牧羊犬","母");

        list.add(animal);
        list.add(animal1);
        for (int i = 0; i < list.size(); i++) {
            System.out.println("品种 \t" + list.get(i).getName() + "性别\t" + list.get(i).getSex());
        }
    }
}

  

Car 类

package com.renzen.Animal.Day1;

public class Car {
    private String name;
    private double price;

    //无参构造器
    public Car() {
    }


    //有参构造器
    public  Car(String name,double price){
        //如果不用this  则name不能给name赋值
        //如果不用this  则price不能给price赋值
        //name=name;
        //price=price;

        this.name=name;
        this.price=price;
    }

    //run
    public void run(String name){
        System.out.println(this.name+"在和"+name+"比赛");
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

Test

package com.renzen.Animal.Day1;

public class Test1 {
    public static void main(String[] args) {
        Car c1=new Car("张三",121212);
        //当类名中不用this指定时
        System.out.println(c1.getName());//null
        System.out.println(c1.getPrice());//0.0

        System.out.println(c1.getName());//张三
        System.out.println(c1.getPrice());//121212

        c1.run("宝马");
    }
}

 封装 个人 理解 就是 private 私有化成员属性  对外暴露set/get方法堆私有属性进行修改

Person类

package com.renzen.Animal.Day1;

public class Person {
    private int age;

    //无参构造器
    public Person(){

    }
    //有参构造器
    public void Person(int age){
        this.age=age;
    }

    //get set
    public void setAge(int age){
        if(age>0 && age<100){
            this.age=age;
        }else{
            System.out.println("age输入值有问题");
        }
    }
    public int getAge(){
        return this.age;
    }
}

Test类、

package com.renzen.Animal.Day1;

public class Test3 {
    public static void main(String[] args) {
        Person p=new Person();
        System.out.println(p.getAge());//0

        p.setAge(18);
        System.out.println(p.getAge());//18
    }
}