编写for-each循环来从ArrayList中获取对象 [英] Writing a for-each loop to get objects from an ArrayList
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问题描述
for(Obj o:ArrayList< Obj> )
在这个例子中:
class Car {
int number;
public Car(int num){number = num; }
int getNumber(){return this.number; }
}
class CarPark {
ArrayList< Car>汽车;
public CarPark(){cars = new ArrayList< Car>(); }
public class main {
public static void main(String [] args){
CarPark p = new CarPark();
p.add(新车(123));
p.add(新车(456));
p.add(新车(789)); (Car c:p.cars){
System.out.println(c.getNumber());
$ b 如何编写循环?这个语法是否可能?
解决方案
您的for-each循环没有问题。
你必须修改一点。要添加新的 Car
对象到 ArrayList
,使用 p.cars.add )
。
public static void main(String [] args){
CarPark p =新的CarPark();
p.cars.add(new Car(123));
p.cars.add(新车(456));
p.cars.add(new Car(789)); (Car c:p.cars){
System.out.println(c.getNumber());
$ ArrayList cars
是 CarPark
类对象的成员 p
,你可以通过 p.cars
来访问它。
I want to write a for loop using the for-each syntax:
for(Obj o : ArrayList<Obj>)
As in this example:
class Car{
int number;
public Car(int num){ number = num; }
int getNumber(){ return this.number; }
}
class CarPark{
ArrayList<Car> cars;
public CarPark(){ cars = new ArrayList<Car>(); }
}
public class Main{
public static void main(String[] args){
CarPark p = new CarPark();
p.add(new Car(123));
p.add(new Car(456));
p.add(new Car(789));
for(Car c : p.cars){
System.out.println(c.getNumber());
}
}
}
How do I write the loop? Is this syntax possible?
解决方案 Your for-each loop has no problem.
There is just one point you must modify. To adding new Car
objects to ArrayList
, use p.cars.add()
.
public static void main(String[] args) {
CarPark p = new CarPark();
p.cars.add(new Car(123));
p.cars.add(new Car(456));
p.cars.add(new Car(789));
for (Car c : p.cars) {
System.out.println(c.getNumber());
}
}
So the ArrayList
cars
is a member of CarPark
class object p
, that you can access it through p.cars
.
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