Java 游戏的每一次迭代我都想让它的生命周期减少1
所以我有一个arraylist,它存储关于宇宙的不同物体(行星、彗星、恒星等)。而不是这样做:Java 游戏的每一次迭代我都想让它的生命周期减少1,java,object,arraylist,Java,Object,Arraylist,所以我有一个arraylist,它存储关于宇宙的不同物体(行星、彗星、恒星等)。而不是这样做: planet.decreaseLifeTime(1); star.decreaseLifeTime(1); comet.decreaseLifeTime(1); 游戏的每一次迭代我都想让它的生命周期减少1。我试过这个,但不起作用: private ArrayList<SpaceObject> universeEntities; public void reduceLifeTime()
planet.decreaseLifeTime(1);
star.decreaseLifeTime(1);
comet.decreaseLifeTime(1);
游戏的每一次迭代我都想让它的生命周期减少1。我试过这个,但不起作用:
private ArrayList<SpaceObject> universeEntities;
public void reduceLifeTime() {
for (SpaceObject entity: universeEntities) {
entity.decreaseLifeTime(1);
if(entity.getLifeTime() <= 0) {
erase(entity);
System.out.println("This entity has been erased");
}
System.out.println("life time: " + entity.getLifeTime());
}
}
如果erase(entity)
正在修改universeEntities列表,java会发疯
您可以将要擦除的SpaceObject存储在单独的列表中,然后在for循环后将其擦除
或
您可以在universeEntities上循环,而无需使用迭代器
e、 g.数字索引根据您对
reduceLifeTime
方法的实现,问题可能在于调用其中的erase
方法(取决于如何实现)
如果erase
方法只是试图通过调用ArrayList的方法从universeEntities
集合中删除一个项,那么它只是破坏了一个迭代器
考虑重新实现您的方法以:
public void reduceLifeTime() {
Iterator<SpaceObject> iterator = universeEntities.iterator();
while (iterator.hasNext()) {
SpaceObject object = iterator.next();
object.decreaseLifeTime(1);
if(object.getLifeTime() <= 0) {
iterator.remove();
System.out.println("This entity has been erased.");
}
System.out.println(String.format("Life time: %d", object.getLifeTime()));
}
}
public void reduceLifeTime(){
迭代器迭代器=universeEntities.Iterator();
while(iterator.hasNext()){
SpaceObject object=iterator.next();
对象。寿命递减(1);
如果(object.getLifeTime(),你的问题是什么?行擦除(实体)
是否更改universeEntities
列表?用一个循环围绕它显示完整的代码,而不是“完整的代码”,但这是我开始编程时犯的一个错误,我仍然偶尔会忘记删除某个项会扰乱迭代周期。但请详细说明他执行擦除的方式有什么问题,以及到底是什么让Java对此感到“疯狂”。根据Java API文档[API 2014]如果在迭代过程中修改了基础集合,则未指定迭代器的行为。这在删除迭代器当前指向的项时尤为重要。几乎每个iterable的实现都会遇到此问题。
public void reduceLifeTime() {
Iterator<SpaceObject> iterator = universeEntities.iterator();
while (iterator.hasNext()) {
SpaceObject object = iterator.next();
object.decreaseLifeTime(1);
if(object.getLifeTime() <= 0) {
iterator.remove();
System.out.println("This entity has been erased.");
}
System.out.println(String.format("Life time: %d", object.getLifeTime()));
}
}
public class Test {
private ArrayList<SpaceObject> universeEntities = new ArrayList<SpaceObject>();
public Test() {
universeEntities.add(new Planet());
universeEntities.add(new Planet());
}
public void reduceLifeTime() {
Iterator<SpaceObject> iterator = universeEntities.iterator();
while (iterator.hasNext()) {
SpaceObject object = iterator.next();
object.decreaseLifeTime(1);
if(object.getLifeTime() <= 0) {
iterator.remove();
System.out.println("This entity has been erased.");
}
System.out.println(String.format("Life time: %d", object.getLifeTime()));
}
}
public static void main(String[] args) {
Test test = new Test();
while(true) {
test.reduceLifeTime();
// Endless loop. Need a quit condition.
}
}
public static class SpaceObject {
protected int life = 0;
public SpaceObject(int life) {
this.life = life;
}
public void decreaseLifeTime(int value) {
this.life -= value;
}
public int getLifeTime() {
return life;
}
}
public static class Planet extends SpaceObject {
public Planet() {
super(10);
}
}
}