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How do I get length of list of lists in Java?

stackoverflow.com › questions › 6846841 › how-do-i-get-length-of-list-of-lists-in-java

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<String> sublist : data) {
    // TODO: Null checking
    total += sublist.size();
}
// total is now the total number of strings

Answer from Jon Skeet on Stack Overflow

Scaler

scaler.com › home › topics › java list size()

Java List Size() - Scaler Topics

April 28, 2024 - When we call the size() method on the list; it returns 4. Since the size() method returns the value stored in the size variable, it will be a constant-time operation. We can use the same size() method to get the number of elements stored in a hashset in java.

Stack Overflow

stackoverflow.com › questions › 6846841 › how-do-i-get-length-of-list-of-lists-in-java

How do I get length of list of lists in Java? - Stack Overflow

Top answer

1 of 4

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<String> sublist : data) {
    // TODO: Null checking
    total += sublist.size();
}
// total is now the total number of strings

2 of 4

Java 8

import java.util.Arrays;
import java.util.List;
import java.util.ArrayList;

public class HelloWorld{

     public static void main(String []args){
            List<List<String>> stringListList = new ArrayList<>();
            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 -> i.size()).sum();

            System.out.println("stringListList count: "+count);
     }
}

Discussions

java - Initial size for the ArrayList - Stack Overflow

Actually, its not obvious from the docs that a list needs to have at least n items added before you can set/add item n-1. ... Perception: I don't know if it is obvious, but it is specified. One has to read JavaDoc carefully.Throws: IndexOutOfBoundsException - if index out of range (index < 0 || index >= size... More on stackoverflow.com

stackoverflow.com

How to get array list size in java jsp?

You can use the .size() method of your ArrayList https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html If you do not need the number of the element and only need the element value then you could skip that and just use the enhanced for statement. https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html More on reddit.com

r/javahelp

November 16, 2014

What is the maximum size of a bitset in Java?

Most likely it would be the same max size as arrays have, which is VM-dependent, but seems to be close to Integer.MAX_VALUE. The reason I say this is because this seems to be basically a List with some special bit-related functionality. So it's likely implemented to store these bits in an array internally; if it is storing them as a single element in the array it would make sense that you can't have more than the maximum number of elements in the array. Edit: looking at the implementation , I'm not sure what the limit is. They use an array of longs to store the data, so...maybe it would support more? That said, the get and set take integers for indexes, so even if you could support more, you couldn't pass an index to the functions larger than Integer.MAX_VALUE. More on reddit.com

r/learnprogramming

September 22, 2019

[JAVA] Why is my ArrayList size always 0

Your ArrayList contains 0 elements, so the size is 0. Your top is also initially -1, so the expression top == stack.size() - 1 will evaluate to -1 == 0 - 1, which is always true (until something is added to the stack). You may be confusing size (number of elements in the current ArrayList) with the capacity (maximum number of elements allowed in the current ArrayList). In any case, if you're trying to write a stack for learning purposes, you'd probably get more out of it if you implemented it on a more basic level, and used an array internally instead of an ArrayList which basically has already implemented most of the logic for you. Alternatively, if you just need a stack, you should probably use java.util.Stack instead of re-implementing one. More on reddit.com

r/learnprogramming

February 26, 2017

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