Java练习代码（1）---多态，抽象类，静态类/变量，接口，异常处理

本文章是我个人对JAVA基础概念的一个复习的练习代码，里面涉及了面对对象编程：多态，抽象类，静态类/变量，接口。还有错误处理的技术。

1.为主函数

package test_duotai;

public class test3 
{
    public static void main(String [] args) 
    {
        Panzer4 d = new Panzer4(25,75,"d",40);//声明类
        System.out.println(d.getType());
        d.move_1();
        Panzer4.tank_fire();//因为这个方法是静态的，所以要这样调用
        Panzer4 d1 = new Panzer4(25,75,"d",40);
        Panzer4.asd += 1;//asd是一个未被封装的静态变量
        d1.engine();
        try //异常处理，除非值是20都会被catch
        {
            d.enter_num(21);
            
        }
        catch(try_catch_tank e) 
        {
            System.out.println("you have to enter 20 to avoid this error ." + e.get_error(21));
            e.printStackTrace();
        }
    }
}

2.抽象类Tank，被Panzer4继承

package test_duotai;

public abstract class Tank 
{
    private int ammo;
    private int armor;
    private String type;
    
    
    public Tank(int ammo,int armor,String type)
    {
        System.out.println("Constructing an Tank");
        this.ammo = ammo;
        this.armor = armor;
        this.type = type;
    }
    
    public String getType()
    {
        return type;
    }
    public int getammo()
    {
        return ammo;
    }
    public void setammo(int ammo_in)
    {
        ammo = ammo_in;
    }
    public int getarmor()
    {
        return armor;
    }    
    
    
    public abstract void move_1();//抽象方法，由子类定义
    
    public static void tank_fire() //静态方法
    {
        System.out.println("Boom!");
    }
}

3.接口

package test_duotai;

public interface moblie { //接口要求Panzer4定义两个类
    public void engine();
    public void gas();

}

4.子类，继承了Tank,调用了moblie接口。

package test_duotai;

public class Panzer4 extends Tank implements moblie
{
    private int supercharge;
    public static int asd = 30;//静态变量，供所有的panzer4实例使用。
    public Panzer4(int ammo,int armor,String type,int supercharge)
    {
        
        super(ammo,armor,type);
        
        set_super(supercharge);
        
    }    
    public void set_super(int supercharge_in)
    {
        supercharge = supercharge_in;
    }
    public void move_1()
    {
        System.out.println("Panzer 4 on the move");
    }
    public void use_super()
    {
        System.out.println("fire supercharge : " +  supercharge);
    }    
    public void engine() 
    {
        System.out.println("fire engine");
    }
    public void gas() 
    {
        System.out.println("gas");
    }
    public int enter_num(int test_num) throws try_catch_tank
    {
        if (test_num == 20) 
        {
            
        }
        else 
        {
            throw new try_catch_tank(test_num);
            
        }
        return test_num;
    }
}

5.异常处理

package test_duotai;

public class try_catch_tank extends Exception 
{
    int test_num;
    public try_catch_tank(int test_num)
    {
        this.test_num = test_num;
    }
    public int get_error(int test_num)
    {
        return test_num;
    }

}