Question

我有arraylists，我只想在各自的arrayList中连接关于其索引的项目。下面的粗略代码块解释了我想要实现的更多内容。 EDITED

List<String> list1 = new Arraylist<String>();
List<String> list2 = new Arraylist<String>();
List<String> list3 = new Arraylist<String>();

list1.add("list11");
list1.add("list12");
list1.add("list13");

list2.add("list21");
list2.add("list22");


list3.add("list31");
list3.add("list32");
list3.add("list33");
list3.add("list34");  


List<ArrayList<String>> container = new ArrayList<ArrayList<String>>();
container.add(list1);
container.add(list2);
container.add(list3);

List<String> finalList  = new Arraylist<String>();

void concatMax(container){

}

//result finalList contents
list11 list21 list31 //- first item
list12 list22 list32 //- second item
list13 ------ list33 //- third item
------ ------ list34 //- forth item


void concatMin(container){

}

 //result inalList contents
list11 list21 list31 //- first item
list12 list22 list32 //- second item

Answer 1

替换

container.add(list1); container.add(list2); container.add(list3);

与

container.addAll(list1); container.addAll(list2); container.addAll(list3);

~~然后容器将是你期望的finalList（至少这是我认为你的意思）~~

编辑：

最大：

int max = 0;
for (ArrayList<String> l : container) max = Math.max(max, l.size());

for (int i = 0; i < max; i++) {
    String s = "";
    for (ArrayList<String> l : container) {

        if (i < l.size) {
            s += l.get(i) + " ";
        } else {
             s += "------ ";
        }
    }
    finalList.add(s);
}

（分钟）：

int min = Integer.MAX_VALUE;
for (ArrayList<String> l : container) min = Math.min(min, l.size());

for (int i = 0; i < min; i++) {
    String s = "";
    for (ArrayList<String> l : container) {
        s += l.get(i) + " ";
    }
    finalList.add(s);
}

Answer 2

在我看来，您正在寻找的是transpose()函数，该函数可用于列表列表

public static void main(String[] args) {
    List<String> list1 = new ArrayList<String>();
    List<String> list2 = new ArrayList<String>();
    List<String> list3 = new ArrayList<String>();

    list1.add("list11");
    list1.add("list12");
    list1.add("list13");

    list2.add("list21");
    list2.add("list22");

    list3.add("list31");
    list3.add("list32");
    list3.add("list33");
    list3.add("list34");

    List<List<String>> container = new ArrayList<List<String>>();
    container.add(list1);
    container.add(list2);
    container.add(list3);

    printList(container);
    List<List<String>> transposed = transpose(container);
    printList(transposed);

}

private static void printList(List<List<String>> transposed) {
    for (List<String> list : transposed) {
        System.out.println(list);
    }
    System.out.println("---------------");
}

private static List<List<String>> transpose(List<List<String>> container) {
    List<List<String>> newList = new ArrayList<List<String>>();
    int max = getMax(container);
    int i = 0;
    for (List<String> list : container) {
        for (int j = 0; j < max; j++) {
            String string =j<list.size()?list.get(j):null;
            setList(i, string, getList(newList, j));
        }
        i++;
    }
    return newList;
}

private static int getMax(List<List<String>> container) {
    int max=0;
    for (List<String> list : container) {
        max = Math.max(list.size(), max);
    }
    return max;
}

private static void setList(int i, String string,
        List<String> newInnerList) {
    if (i >= newInnerList.size()) {
        newInnerList.add(string);
    } else {
        newInnerList.set(i, string);
    }
}

private static List<String> getList(List<List<String>> list, int j) {
    List<String> innerList;
    if (j >= list.size()) {
        innerList  = new ArrayList<String>();
        list.add(innerList);
    }else{
        innerList = list.get(j);
    }
    return innerList;
}

<强>输出

[list11, list12, list13]
[list21, list22]
[list31, list32, list33, list34]
---------------
[list11, list21, list31]
[list12, list22, list32]
[list13, null, list33]
[null, null, list34]
---------------

如何在java中连接多个arraylists的第一，第二，第三等

2 个答案: