（1）創建一個叫做機動車的類： 屬性：車牌號(String)，車速(int)，載重量(double) 功能：加速(車速自增)、減速(車速自減)、修改車牌號，查詢車的載重量。 編寫兩個構造方法：一個沒有形參，在方法中將車牌號設置“XX1234”，速 度設置為100，載重量設置為100；另一個能為對象的所有屬性賦值； （2）創建主類： 在主類中創建兩個機動車對象。

package a;

public class Jidongche {
    private String chepaihao;
    private int chesu;
    private double zaizhong;
    public String getChepaihao() {
        return chepaihao;
    }
    public void setChepaihao(String chepaihao) {
        this.chepaihao = chepaihao;
    }
    public int getChesu() {
        return chesu;
    }
    public void setChesu(int chesu) {
        this.chesu = chesu;
    }
    public double getZaizhong() {
        return zaizhong;
    }
    public void setZaizhong(double zaizhong) {
        this.zaizhong = zaizhong;
    }
    public Jidongche()
    {
        chepaihao="XX231";
        chesu=100;
        zaizhong=100;
    }
    public Jidongche(String chepaihao, int chesu, double zaizhong) {
        super();
        this.chepaihao = chepaihao;
        this.chesu = chesu;
        this.zaizhong = zaizhong;
    }
    public void jiasu(int sudu)
    {
        if(sudu<0)
        {
            System.out.println("無法加速");
        }
        else
        {
           chesu+=sudu;
        }
    }
    public void jiansu(int sudu)
    {
        if(sudu<0)
        {
            System.out.println("無法減速");
        }
        
        else
        {
           
           if((chesu-sudu)<0)
           {
               System.out.println("減速失敗");
           }
           else
           {
               chesu-=sudu;
           }
               
        }
    }

}

package a;

public class Che {

    public static void main(String[] args) {
    Jidongche che1=new Jidongche();
    che1.setChepaihao("遼A9752");
    che1.jiasu(30);
    System.out.println("車牌號="+che1.getChepaihao());
    System.out.println("當前車速="+che1.getChesu());
    System.out.println("載重="+che1.getZaizhong());
    
    Jidongche che2=new Jidongche("遼B5086",150,200);
    che2.jiansu(20);    
    System.out.println("車牌號="+che2.getChepaihao());
    System.out.println("當前車速="+che2.getChesu());
    System.out.println("載重="+che2.getZaizhong());
    
    }

}