Question

我试图制作一个arraylists的arraylist。我的代码到处都是，我刚刚添加了东西并尝试错误试用。最后我要做的就是说，我有一辆车...它有速度，里程，英里每小时，如果他们想买它，就把它添加到arraylists的arraylist，然后能够获取所拥有汽车的清单，只是为了让您了解我想要做的事情。 idk如果它有帮助，或者可能有更好的方法。我只需要内部数组的迭代帮助，其余的我可以搞清楚。现在它只是迭代主要的arraylist并显示那里看起来像一个数组的一切。我宁愿使用for循环然后迭代类，但它如何工作对我有好处。

public class Thelist {

    String a ="aa";
    String b ="bb";
    String c ="cc";

    static ArrayList<ArrayList<String>> collection = new ArrayList<ArrayList<String>>();
    static int count=0;
    ArrayList<String> listOfSomething1 = new ArrayList<String>();

    public void gg(){

    ArrayList<String> listOfSomething1 = new ArrayList<String>();
    listOfSomething1.add(a);
    listOfSomething1.add(b);
    listOfSomething1.add(c);

    collection.add(listOfSomething1);    
    count++;    
    }

    public void jk(int u){

    //this one feel like i can make new arraylist and use for loop for the collection size and iterate each one
    //but seems pretty hacky to me

        ArrayList<String> lis = new ArrayList<String>();
        lis.addAll(collection.get(u));

        for(int i=0;i<lis.size();i++ ){
          System.out.println("each "+i+" "+lis.get(i));
        }       
    }

    public void ll(){
        System.out.println(collection.size());
        System.out.println(collection.get(0).size());
    }

    public void ccc(String x,String y, String z){
        this.a= x;
        this.b=y;
        this.c=z;
    }

    public void remo(int r){

        collection.remove(0);
        count--;
    }

    public void getcount(){

        System.out.println("the count "+count); 

    }

    public void showall(){

        //this one shows all of the arraylist as arrays it looks like to me, I want each element
        // feel like i should be able to add another for loop to iterate over listOfSomething1
        //which is be add to the collection arraylist
        // but it don't work tryed for each too
        for(int i=0;i < collection.size();i++){
            System.out.println("uoo "+collection.get(i));

        }
    }
}






public class MainActivity extends Activity {

static int oo = 1;

Thelist ll = new Thelist();


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);   

}

public void woow(View v){

     String gg = Integer.toString(oo);
     ll.ccc("phi"+gg, "phil"+gg, "phily"+gg);   
     ll.gg();       
     oo++;
}


public void shoo(View v){

ll.showall();   
}

}

Answer 1

只需使用两个嵌套的for循环。第一个迭代集合，每次迭代产生一个ArrayList<String>。获取此列表并在第二次迭代中迭代它。为简单起见，您可以在此处使用for-each循环：

for(ArrayList<String> cars : collection) {
    for(String car : cars) {
        System.out.println(car);
    }
}

Answer 2

   public void showall(){

        for(int i=0;i < collection.size();i++)
            for(int j=0; j< collection.get(i).size();j++)
              System.out.println(collection.get(i).get(j));

        }

arraylists的arraylist的内部arraylist的交互

2 个答案: