[英]Removing objects from an array(Java)
我有一个所有者类,其中包含一系列拥有的狗。 它看起来像这样:
public class Owner {
private String ownerName;
public Dog[] ownedDogs = new Dog[0];
private int dogCount = -1;
public Owner(String ownerName) {
this.ownerName = ownerName;
}
public String getName(){
return ownerName;
}
public void assignDog(Dog d) {
Dog[] newOwnedDogs = new Dog[ownedDogs.length + 1];
for (int i = 0; i < ownedDogs.length; i++) {
newOwnedDogs[i] = ownedDogs[i];
}
ownedDogs = newOwnedDogs;
this.ownedDogs[++dogCount] = d;
makeOwner(this, d);
}
private void makeOwner(Owner o, Dog d) {
if(d.owner !=o) {
d.owner = o;
}
}
public boolean ownerOfDog(Dog d){
if (d.getOwner() == this){
return true;
} else {
return false;
}
}
public String toString(){
return "Name: " + ownerName;
}
狗类看起来像这样:
public class Dog{
private String name;
private String breed;
private int age;
private int weight;
private double tailLength;
public Owner owner;
public Dog(String name, String breed, int age, int weight) {
this.name = name;
this.breed = breed;
this.age = age;
this.weight = weight;
}
public String getName() {
return name;
}
public String getBreed() {
return breed;
}
public void increaseAge() {
age++;
}
public int getAge() {
return age;
}
public int getWeight() {
return weight;
}
public double getTailLength() {
if (breed.equalsIgnoreCase("dachshund") || breed.equalsIgnoreCase("tax")) {
return 3.7;
} else {
return weight * (age / 10.0);
}
}
public Owner getOwner(){
return owner;
}
public void setOwner(Owner o) {
if(this.owner != o) {
this.owner = o;
o.assignDog(this);
}
}
public String toString() {
return "Name: " + name + " Breed: " + breed + " Age: " + age + " Weight: " + weight + " Tail length: " + getTailLength() + " owned by: " + owner;
}
}
我正在尝试创建一种从数组中删除狗的方法,这就是我目前拥有的:
public void removeDog () {
System.out.println("Enter the name of the dog?> ");
String name = input.nextLine();
Owner o = findOwner(name);
Dog d = findDog(name);
if(d == null) {
System.out.println("Error: no such dog");
} else {
//Code to remove dog from o.ownedDogs
}
System.out.println(name + " is removed from the register");
}
有没有一种不用手动输入元素索引就可以从数组中删除对象的好方法? 我看过使用其他数据类型的示例,但我是 Java 的初学者,所以在这里应用它时遇到了麻烦。
使用数组的问题是删除一个实际上并不重要的对象,因为您必须:
与以下内容相比,这一切都“太难了”:
public List<Dog> ownedDogs = new ArrayList<>();
然后
ownedDogs.remove(d);
您需要在Dog
类中实现equals()
(和hashCode()
)。
作为一般规则,当您可以使用集合时,永远不要使用数组。
您可能应该使用Set<Dog> ownedDogs = new HashSet<>();
并将ownedDogs
私有并为其提供吸气剂。
从功能的角度来看,假设在你的例子中,狗的名字是一个唯一的标识符,你将通过过滤初始数组来生成一个新数组:
ownedDogs = Arrays.stream(ownedDogs)
.filter(dog -> !dog.name.equals(nameToRemove))
.toArray();
Arrylists 会解决这个问题,它可以像这样实现
public ArrayList<Dog> ownedDogs=new ArrayList<>();
并使用
ownedDogs.remove(index);
与常规数组不同,它们没有定义的大小,一旦你从它们中删除一个对象,索引就会相应地发生变化
如果要从数组中删除元素,则不应使用数组。 相反,ArrayList 可能适合您的需求,因为您可以非常轻松地添加和删除狗。
鉴于您使用 ArrayList,这里有一种方法可以从所述列表中删除一只狗:
for (int i = 0; i < ownedDogs.size(); i++){
if(d == ownedDogs.get(i)){
ownedDogs.remove(i);
break;
}
}
要么:
ownedDogs.remove(d)
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