java 如何打印 ArrayLists 的 ArrayList，以便每个内部列表都打印在一行上？
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How to print an ArrayList of ArrayLists so that each inner list is printed on one row?
提问by Anurag Ramdasan
I have an ArrayList of ArrayLists - something like ArrayList<ArrayList<Node>>.
Since I get this as a return value from a function, after every call a different size is called. I am wondering how to display its elements is such a way that the inner ArrayList constitutes one row and so for every row.
我有一个 ArrayLists 的 ArrayList - 类似于ArrayList<ArrayList<Node>>. 由于我将其作为函数的返回值获取，因此每次调用后都会调用不同的大小。我想知道如何以内部 ArrayList 构成一行的方式显示其元素，因此对于每一行。
What would be my required parameter(s) for the for loop? Thanks in advance.
for 循环所需的参数是什么？提前致谢。
回答by giorashc
for (List<Node> l1 : arrayLists) {
for (Node n : l1) {
System.out.print(n + " ");
}
System.out.println();
}
回答by Luiggi Mendoza
Here is a basic sample:
这是一个基本示例：
public static void main(String[] args) {
List<List<String>> ls;
//initialize ls and set values in it...
//after set some values, let's print it
for(List<String> innerLs : ls) {
String[] arr = innerLs.toArray();
System.out.println(Arrays.deepToString(arr));
}
}
It should be the same logic for List<List<T>>.
应该是相同的逻辑List<List<T>>。
回答by Chandra Sekhar
invoke iterator()which will return an Iterator<ArrayList<Node>>, and loop on that.
invokeiterator()将返回一个Iterator<ArrayList<Node>>, 并在其上循环。
Inside the loop invoke iterator()again, on each iterated elements, which will return a Iterator<Node>; use an inner loop and use next()on it to display.
在循环内部iterator()再次调用，在每个迭代元素上，这将返回一个Iterator<Node>; 使用内循环并使用next()它来显示。
For the loops use either a 'foreach' loop (for(Node n : iterator)) or a while loop (while(iterator.hasNext())).
对于循环，使用“foreach”循环 ( for(Node n : iterator)) 或 while 循环 ( while(iterator.hasNext()))。
