//這是父類(lèi)貨車(chē)的代碼
public?class?Truck?{

?static?Float?cargoCa;?????//創(chuàng)建貨車(chē)的載貨量

?static?int?capacity=4;????//創(chuàng)建貨車(chē)的載客量

?static?int?rent;?????//創(chuàng)建貨車(chē)的日租金

?int?smallType;?????//用來(lái)接收局部變量smalltype的值

?Scanner?input=new?Scanner(System.in);

?void?getType()?{

??System.out.println("請(qǐng)輸入您要選擇的貨車(chē)類(lèi)型：");

?????System.out.println("1、輕型貨車(chē)（可核載5噸）??????????2、重型貨車(chē)（可核載20噸）");

?????int?smalltype=input.nextInt();

?????smallType=smalltype;

?????while(smalltype*0==0)?{

???????if(smalltype==1)?{???//這部分重型貨車(chē)的繼承代碼沒(méi)有貼上

????????Heavy?heavy=new?Heavy();

????????heavy.getBrand();

????????break;

???????}else?if(smalltype==2)?{

????????Light?light=new?Light();

????????light.getBrand();

????????break;

???????}else?{

????????System.out.println("您的輸入有誤！請(qǐng)輸入您要選擇的貨車(chē)類(lèi)型：");

????????System.out.println("1、輕型貨車(chē)（可核載5噸）??????????2、重型貨車(chē)（可核載20噸）");

????????smalltype=input.nextInt();

???????}

?????}

?}
?
//show()方法調(diào)用兩個(gè)輕貨和重貨子類(lèi)的showFinal()方法展示租車(chē)清單
?void?show()?{?????

??if(smallType==1)?{

??????Light?light=new?Light();

??????light.showFinal();

??}else?if(smallType==2)?{

???Heavy?heavy=new?Heavy();

???heavy.showFinal();

??}

?}

}

??

??//這是子類(lèi)Light繼承父類(lèi)Truck的代碼

??public?class?Light?extends?Truck?{

?static?String?name="輕型貨車(chē)";
?
?//【注意，創(chuàng)建light字符串，用來(lái)接收局部變量中的品牌名稱(chēng)】
?static?String?light;

?Scanner?input=new?Scanner(System.in);

?void?getBrand()?{

??String?light1="日產(chǎn)";

??String?light2="雪鐵龍";

??String?light3="標(biāo)致";

??Light.cargoCa=5f;

??System.out.println("請(qǐng)輸入您要選擇的輕型貨車(chē)品牌：");

?????System.out.println("1、"+light1+"（1200元/天）??????????"+"2、"+light2+"（1500元/天）??????????"+"3、"+light3+"（1800元/天）");

?????int?lBrand=input.nextInt();

?????while(lBrand*0==0)?{

??????if(lBrand==1)?{

???????Light.rent=1200;

???????light=light1;

???????break;

??????}else?if(lBrand==2)?{

???????Sedan.rent=1500;

???????light=light2;

???????break;

??????}else?if(lBrand==3)?{

???????Sedan.rent=1800;

???????light=light3;

???????break;

??????}else?{

???????System.out.println("您的輸入有誤！請(qǐng)輸入您要選擇的輕型貨車(chē)品牌：");

???????System.out.println(light1+"（1200元/天）??????????"+light2+"（1500元/天）??????????"+light3+"（1800元/天）");

???????lBrand=input.nextInt();

??????}

?????}

?}
?
//子類(lèi)Light用來(lái)展示租車(chē)清單的showFinal()方法
?void?showFinal()?{

??System.out.println("請(qǐng)輸入您要租車(chē)的數(shù)量：");

?????int?amt=input.nextInt();

??System.out.println("請(qǐng)輸入您要租車(chē)的天數(shù)：");

?????int?days=input.nextInt();

?????int?price=Light.rent*amt*days;
?????
?????//【注意，就是這里的變量light，在InitialCRS類(lèi)里面的最后輸出結(jié)果為null】
?????System.out.println("車(chē)型："+light+name);

?????System.out.println("總載人量："+Truck.capacity*amt+"??????????總載貨量："+Light.cargoCa*amt+"噸");

?????System.out.println("總計(jì)："+price+"元");

?}

}



?//這是執(zhí)行類(lèi)InitialCRS的代碼????????
?public?class?InitialCRS?{

?public?static?void?main(String[]?args)?{

??//?TODO?Auto-generated?method?stub

??Scanner?input=new?Scanner(System.in);

??System.out.println("請(qǐng)問(wèn)您是否要租車(chē)？");

??System.out.println("1、是??????????2、否");

??int?confirm=input.nextInt();

??while(confirm*0==0)?{

??????if(confirm==2)?{

???????System.out.println("答答租車(chē)系統(tǒng)已退出，感謝您的使用！");

???????break;

??????}else?if(confirm==1)?{

????System.out.println("請(qǐng)選擇您要租賃的車(chē)輛類(lèi)型：");

???????System.out.println("1、汽車(chē)??????????2、貨車(chē)??????????3、皮卡");

???????int?type=input.nextInt();

???????while(type*0==0)?{

????????????if(type==1)?{???//Car父類(lèi)部分的代碼沒(méi)有貼出

????????????Car?car=new?Car();

????????????car.getType();

????????????car.show();

????????????break;

????????????}else?if(type==2)?{???//本次問(wèn)題中的Truck類(lèi)的方法調(diào)用

???????Truck?truck=new?Truck();

???????truck.getType();

???????truck.show();

???????break;

?????????????}else?if(type==3)?{???//pickup部分的代碼沒(méi)有貼出

????????Pickup?pickup=new?Pickup();

????????pickup.getBrand();

????????pickup.show();

????????break;

??????????????}else?{

????????????System.out.println("您的輸入有誤！請(qǐng)選擇您要租賃的車(chē)輛類(lèi)型：");

????????????System.out.println("1、汽車(chē)??????????2、貨車(chē)??????????3、皮卡");

????????????type=input.nextInt();

????????????}

???????}

???????break;

??????}else?{

???????System.out.println("您的輸入有誤！請(qǐng)問(wèn)您是否要租車(chē)？");

???????System.out.println("1、是??????????2、否");

???????confirm=input.nextInt();

???????}

?????}

??input.close();

?}

}
//在這里多說(shuō)一句，我在其它子類(lèi)里邊，以一模一樣的方式創(chuàng)建了類(lèi)似于light的用來(lái)接收品牌的字符串，其最后的輸出結(jié)果都是正常的，只有這個(gè)字符串light不知道怎么回事輸出結(jié)果竟然是null

?