Java 如何遍历对象的 ArrayList 的对象的 ArrayList？
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How to iterate through an ArrayList of Objects of ArrayList of Objects?
提问by user3437460
Using an example:
使用示例：
Let say I have a class call Gun.
I have another class call Bullet.
假设我有一个班级电话Gun。我还有一个班级电话Bullet。
Class Gunhas an ArrayList of Bullet.
类Gun有一个 ArrayList Bullet。
To iterate through the Arraylist of Gun..instead of doing this:
要遍历Gun..的 Arraylist 而不是这样做：
ArrayList<Gun> gunList = new ArrayList<Gun>();
for (int x=0; x<gunList.size(); x++)
System.out.println(gunList.get(x));
We can simply iterate through the ArrayList of Gunas such:
我们可以简单地遍历 ArrayListGun如下：
for (Gun g: gunList) System.out.println(g);
Now, I want to iterate and print out all Bulletof my 3rd Gunobject:
现在，我想迭代并打印出Bullet我所有的第三个Gun对象：
for (int x=0; x<gunList.get(2).getBullet().size(); x++) //getBullet is just an accessor method to return the arrayList of Bullet
System.out.println(gunList.get(2).getBullet().get(x));
Now my question is:Instead of using the conventional for-loop, how do I printout the list of gun objects using the ArrayList iteration ?
现在我的问题是：如何使用 ArrayList 迭代打印出枪对象列表，而不是使用传统的 for 循环？
采纳答案by unholysampler
You want to follow the same pattern as before:
您希望遵循与以前相同的模式：
for (Type curInstance: CollectionOf<Type>) {
// use currInstance
}
In this case it would be:
在这种情况下，它将是：
for (Bullet bullet : gunList.get(2).getBullet()) {
System.out.println(bullet);
}
回答by Tsotne Tabidze
for (Bullet bullet : gunList.get(2).getBullet()) System.out.println(bullet);
回答by 0-4930-42390eo23o2e0-23oe0-23o
Edit:
编辑：
Well, he edited his post.
好吧，他编辑了他的帖子。
If an Object inherits Iterable, you are given the ability to use the for-each loop as such:
如果一个对象继承了 Iterable，你就可以像这样使用 for-each 循环：
for(Object object : objectListVar) {
//code here
}
So in your case, if you wanted to update your Guns and their Bullets:
所以在你的情况下，如果你想更新你的枪和他们的子弹：
for(Gun g : guns) {
//invoke any methods of each gun
ArrayList<Bullet> bullets = g.getBullets()
for(Bullet b : bullets) {
System.out.println("X: " + b.getX() + ", Y: " + b.getY());
//update, check for collisions, etc
}
}
First get your third Gun object:
首先得到你的第三个 Gun 对象：
Gun g = gunList.get(2);
Then iterate over the third gun's bullets:
然后迭代第三把枪的子弹：
ArrayList<Bullet> bullets = g.getBullets();
for(Bullet b : bullets) {
//necessary code here
}
回答by Thorn
We can do a nested loop to visit all the elements of elements in your list:
我们可以做一个嵌套循环来访问列表中元素的所有元素：
for (Gun g: gunList) {
System.out.print(g.toString() + "\n ");
for(Bullet b : g.getBullet() {
System.out.print(g);
}
System.out.println();
}
回答by Andrew Orobator
int i = 0; // Counter used to determine when you're at the 3rd gun
for (Gun g : gunList) { // For each gun in your list
System.out.println(g); // Print out the gun
if (i == 2) { // If you're at the third gun
ArrayList<Bullet> bullets = g.getBullet(); // Get the list of bullets in the gun
for (Bullet b : bullets) { // Then print every bullet
System.out.println(b);
}
i++; // Don't forget to increment your counter so you know you're at the next gun
}
回答by Ray A
When using Java8 it would be more easier and a single liner only.
当使用 Java8 时，它会更容易，而且只有一个单行。
gunList.get(2).getBullets().forEach(n -> System.out.println(n));
