如何使用迭代器迭代二维ArrayList？ [英] How to iterate through two dimensional ArrayList using iterator?

问题描述

我想迭代二维 ArrayList ，其中包含使用迭代器的 String 对象。我还想以一种方式迭代，让我选择是否要通过使用 boolean 值水平（行）第一个或垂直（列）进行迭代。我怎样才能在java中实现这个？

I would like to iterate through two dimensional ArrayList which includes String objects using iterator. I also would like to iterate in a way that let me choose whether I want to iterate horizontally(row) first or vertically(column) by using a boolean value. How can I implement this in java?

到目前为止我尝试过的。

What I've tried so far.

public class IterateThis implements Iterator<String>{
ArrayList<ArrayList<String>> array;

public IterateThis(){
    array = new ArrayList<ArrayList<String>>();
    array.add(new ArrayList<String>());
    array.add(new ArrayList<String>());
    array.add(new ArrayList<String>());
    array.get(0).add("1");
    array.get(0).add("2");
    array.get(0).add("2");
    array.get(1).add("4");
    array.get(1).add("5");
    array.get(1).add("6");
}

Iterator<String> it = array.iterator(); //This gives me an error...why?

我不知道如何实现 boolean 值。

I don't know how I can implement the boolean value though.

推荐答案

行式迭代很简单，如@Awfully Awesome答案所示。

Row-wise iteration is simple as shown in the @Awfully Awesome answer.

尝试了一个列式迭代，假设List总是有 m跨n 元素，其中 m = n

Tried a columnwise iteration with assumption that List will always have m cross n elements where m=n

public static void IterateThis() {
    ArrayList<ArrayList<String>> array = new ArrayList<ArrayList<String>>();
    array.add(new ArrayList<String>());
    array.add(new ArrayList<String>());

    array.get(0).add("1");
    array.get(0).add("2");
    array.get(0).add("2");
    array.get(1).add("4");
    array.get(1).add("5");
    array.get(1).add("6");

    Iterator<ArrayList<String>> it = array.iterator();

    int topLevelIteratorResetCounter = 0;
    int noOfIteratorNextRequired = 1;

    int size = array.size();

    while (it.hasNext()) {

        ArrayList<String> strList = it.next();
        if (noOfIteratorNextRequired > strList.size())
            break;
        Iterator<String> itString = strList.iterator();
        int numtimes = 0;
        String str = null;
        while (numtimes != noOfIteratorNextRequired) {
            str = itString.next();
            numtimes++;
        }
        System.out.println(str);
        numtimes = 0;
        topLevelIteratorResetCounter++;
        if (topLevelIteratorResetCounter == size) { //as column count is equal to column size
            it = array.iterator();  //reset the iterator
            noOfIteratorNextRequired++;
            topLevelIteratorResetCounter = 0;
        }
    }
}

答案使用Iterator。

The answer uses Iterator.

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