Question

我想做类似这样的事情 ArrayList & lt; String< String< String> & gt; my list

我怎样才能创造它?

如何加入外部和内部名单?

如何将内部列表转换为简单的数组列表?

Answer 1

你可以一起走

List<List<String>> ls2d = new ArrayList<List<String>>();
List<String> x = new ArrayList<String>();
x.add("Hello");
x.add("world!");
ls2d.add(x);

System.out.println(Arrays.deepToString(ls2d.toArray()));

Answer 2

第一个阵列列表不是字符串的阵列列表,而是矩阵列表的阵列列表。

ArrayList<ArrayList<String>>

Answer 3

List<List<String>> array = new ArrayList<List<String>>();
...
array.add(new ArrayList<String>())
array.get(0).add("qqq");

数组.get(0) - 是一个内部列表

Answer 4

List<List<String>> super2dArray = new ArrayList<ArrayList<String>>()

这是持有字符串的矩阵列表的矩阵列表。

还有ArrayList< String< String< String>> my list 没有任何意义,因为字符串不是一个收藏/列表,但我认为你理解这一点。未来读者可能不会这样做。

见“https://stackoverflow.com/a/8896608/645270><这个答案 ,以了解为什么我选择左侧有List 。

Answer 5

实现你的愿望有两种方式。我为两者提供代码片断:

1. List<List< String> & gt; lol = 新的ArrayList< List< String> & gt; (;)

Scanner in = new Scanner(System.in);
int size = in.nextInt();

//Declare your two dimensional ArrayList of Strings. 
List< List<String>> lol = new ArrayList<List<String>>();

//Instantiate and Populate
for (int i=0;i<size;i++){
    int internalListSize = in.nextInt(); //the size of each internal list
    lol.add(new ArrayList<String>());
    for (int j=0;j<internalListSize;j++){
        String whateverYouWanttoPut = in.nextLine();
        lol.get(i).add(whateverYouWanttoPut);
    }
}

//Access Elements 
try {
    System.out.println(lol.get(0).get(4));
    System.out.println(lol.get(1).get(2));
    System.out.println(lol.get(3).get(2));
} catch (Exception e){
    System.out.println("ERROR!");
}

2. ArrayList[] 设置 =新的ArrayList[n]; Scanner in = new Scanner(System.in); int size = in.nextInt(); //Declare your two dimensional ArrayList of Strings. ArrayList[] set = new ArrayList[size]; //Populate it. for(int i=0;i<size;i++){ int innerSize = in.nextInt(); set[i] = new ArrayList<String>(); for(int j=0;j<innerSize;j++){ set[i].add(in.nextLine()); } } try{ System.out.println(set[0].get(1)); System.out.println(set[1].get(2)); } catch(Exception e){ System.out.println("ERROR!"); }

Answer 6

尝试一下这个 :

public class JavaTests {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

    String[ ][ ] test2 = new String[3][3];      //3 can be replace if you add more test2[?][?] = "RandomString"

        test2[0][0] = "String1";
        test2[0][1] = "String2";
        test2[0][2] = "String3";

        test2[1][0] = "String4";
        test2[1][1] = "String5";
        test2[1][2] = "String6";

        test2[2][0] = "String7";
        test2[2][1] = "String8";
        test2[2][2] = "String9";

        for (int i = 0; i <= 2; i++){
            for (int j = 0; j <= 2; j++){
                System.out.print(test2[i][j] +"	");
            }
            System.out.println("
");
        }  
        System.out.println("
");      
    }
}

Answer 7

创建 2D 阵列, 如下面 -

原始数据类型的 < 强 > -

int[][] arr = new int[10][10];

用于自定义类的 < em% 强 > -

public class MyClass {
    int x;
    MyClass() { 
        this.x = 0
    }
}

MyClass[][] arr = new MyClass[10][10];
for (int i = 0; i < 10; ++i) {
    for (int j = 0; j < 10; ++j) {
        arr[i][j] = new MyClass();
    }
}

友情链接