不明白一下代碼的 for (car car : carForRent) 為什么是 car car : carForRent
不明白一下代碼的? ? ? for?(car?car?:?carForRent) ? ?為什么是 car car : carForRent? ? ?
car?[?]?carForRent={new?passengerCar(1,"奧迪A4",500,4),new?passengerCar(2,"馬自達6",400,4),
??????????????????????????????????????????new?pickUp(3,"皮卡雪6",450,4,2),new?passengerCar(4,"?金龍?",800,20),
??????????????????????????????????????????new?trunk(5,"松花江",400,4),new?trunk(6,"依維柯",1000,20)};
????????????System.out.println("序號"+"\t"+"汽車名稱"+"\t"+"租金"+"\t"+"\t"+"容量");
????????????
?//打印輸出可供租的汽車清單
????????????for?(car?car?:?carForRent)?{
????????????????//用instanceOf來測試左邊類型的對象是否是右邊類型的實例，返回值為Boolean
????????????????if(car?instanceof?passengerCar){
????????????????????//若它是客車類型的實例，則打印出客車應該有的屬性值，這里注意強轉，否則不會出現(xiàn)
????????????????????//passengerCar類的CarCapacity屬性
????????????????????System.out.println(car.getCarNumber()+"\t"+car.getCarName()+"\t"+car.getCarRentMoney()
??????????????????????????????????????????????????+"/天"+"\t"+"載人:"+((passengerCar)car).getCarCapacity()+"人");
?????????????????????
????????????????}
????????????????if(car?instanceof?pickUp){
????????????????????System.out.println(car.getCarNumber()+"\t"+car.getCarName()+"\t"+car.getCarRentMoney()
??????????????????????????????????????????????????+"/天"+"\t"+"載人:"+((pickUp)car).getCarCapacity()+"人"+"\t"
??????????????????????????????????????????????????+"載貨:"+((pickUp)car).getCarCarryCargo()+"噸");
????????????????}
????????????????if(car?instanceof?trunk){
????????????????????System.out.println(car.getCarNumber()+"\t"+car.getCarName()+"\t"+car.getCarRentMoney()
??????????????????????????????????????????????????+"/天"+"\t"+"載貨:"+((trunk)car).getCarCarryCargo()+"噸");
????????????????}
????????????}
2016-10-25
?for?(Car?car?:?carForRent)這是另一種形式的for循環(huán)，叫foreach，也叫遍歷式循環(huán)
?語法是for(類型 ?變量名 ： 數(shù)組名)，就是每次按順序循環(huán)的從數(shù)組中取值，以你自己定義的變量名car保存，也就是上面寫到的第二個car，第一個Car代表的是這個變量是車這個類型的，在car這個變量中實際上保存的是一個車類型的對象，這個對象就有載貨量、載客量、名字、租金這些屬性，你就可以在這個循環(huán)的過程中每次取出一個對象來操作，打印或者取得你想要的屬性值，它實際上和一般的for循環(huán)
for(int i=0;i=carForRent.length;i++){
????if(carForRent[i] instanceof?passengerCar){
????????????????????//若它是客車類型的實例，則打印出客車應該有的屬性值，這里注意強轉，否則不會出現(xiàn)
????????????????????//passengerCar類的CarCapacity屬性
????????????????????System.out.println(carForRent[i].getCarNumber()+"\t"+carForRent[i].getCarName()+"\t"+
carForRent[i].getCarRentMoney()
??????????????????????????????????????????????????+"/天"+"\t"+"載人:"+((passengerCar)carForRent[i]).getCarCapacity()+"人");?
????????????????}
}實現(xiàn)的效果是一樣的。
2016-10-25
樓上正解