How do I get length of list of lists in Java

Question

If I have a List lt List lt String gt  gt  data in Java  I can get the length of the first list via code   int lengthData   data get 0  size      But how do I get the number of lists in the structure without traversing the list of lists to find out   Maybe I ve been a bit unclear  I have the structure   List lt List lt String gt  gt  data    And I see that   int i   data size      Will equal 1 because it is the root list  So what I want to know is how many sublists there are  Traversal of the structure like this   for  List lt String gt  l   data                              total                         Only gives me a result of 1 which I find odd   I have data of the form   List 1    gt  1  2  3  4 List 2    gt  3  8  9  1   And so on where these are sublists of the root list

User · Answer

Just use  int listCount   data size      That tells you how many lists there are  assuming none are null   If you want to find out how many strings there are  you ll need to iterate   int total   0  for  List lt String gt  sublist   data           TODO  Null checking     total    sublist size         total is now the total number of strings

User · Answer

count of the contained lists in the outmost list int count   data size     lambda to get the count of the contained inner lists int count   data stream   collect  summingInt l - gt  l size

User · Answer

import java util ArrayList  public class TestClass   public static void main String   args         ArrayList lt ArrayList lt String gt  gt  listOLists   new ArrayList lt ArrayList lt String gt  gt         ArrayList lt String gt  List 1   new ArrayList lt String gt         List 1 add  quot 1 quot        List 1 add  quot 2 quot        listOLists add List 1        ArrayList lt String gt  List 2   new ArrayList lt String gt         List 2 add  quot 4 quot        List 2 add  quot 5 quot        List 2 add  quot 10 quot        List 2 add  quot 11 quot        listOLists add List 2       for  int i   0  i  lt  listOLists size    i              System out print  quot list  quot    i    quot    quot            for  int j   0  j  lt  listOLists get i  size    j                  System out print listOLists get i  get j     quot    quot                      System out println                I hope this solution gives a better picture of list if lists

User · Answer

Java 8  import java util Arrays  import java util List  import java util ArrayList   public class HelloWorld        public static void main String   args               List lt List lt String gt  gt  stringListList   new ArrayList lt  gt                 stringListList add Arrays asList new String      0 0      0 1                    stringListList add Arrays asList new String      1 0      1 1      1 2                    stringListList add Arrays asList new String      2 0      2 1                     int count stringListList stream   mapToInt i - gt  i size    sum                 System out println  stringListList count    count

[java] How do I get length of list of lists in Java?

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