Converting List<Integer> to List<String>

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I have a list of integers, List<Integer> and I'd like to convert all the integer objects into Strings, thus finishing up with a new List<String>.

Naturally, I could create a new List<String> and loop through the list calling String.valueOf() for each integer, but I was wondering if there was a better (read: more automatic) way of doing it?

As far as I know, iterate and instantiate is the only way to do this. Something like (for others potential help, since I'm sure you know how to do this):

List<Integer> oldList = ...
/* Specify the size of the list up front to prevent resizing. */
List<String> newList = new ArrayList<>(oldList.size());
for (Integer myInt : oldList) { 
  newList.add(String.valueOf(myInt)); 
}

Python, Python | Convert set into a list. Given a set, write a Python program to convert the given set into list. Examples: Input : {1, 2, 3, 4} Output : [1, 2, 3, 4] Input : {'Geeks'  You can then apply the following syntax in order to convert the list of names to pandas DataFrame: from pandas import DataFrame People_List = ['Jon','Mark','Maria','Jill','Jack'] df = DataFrame (People_List,columns= ['First_Name']) print (df) This is the DataFrame that you’ll get:

Using Google Collections from Guava-Project, you could use the transform method in the Lists class

import com.google.common.collect.Lists;
import com.google.common.base.Functions

List<Integer> integers = Arrays.asList(1, 2, 3, 4);

List<String> strings = Lists.transform(integers, Functions.toStringFunction());

The List returned by transform is a view on the backing list - the transformation will be applied on each access to the transformed list.

Be aware that Functions.toStringFunction() will throw a NullPointerException when applied to null, so only use it if you are sure your list will not contain null.

Python, Given a list of strings, write a Python program to convert each element of the given list into a sublist. Thus, converting the whole list into a list of lists. Examples: In that case, direct type conversion from string to list in Python using the list() method does the job for us. Certainly, if the input string is something like “abcd” , typecasting the string into a list using the list() method gives us a list having the individual characters ‘a’, ‘b’, ‘c’, ‘d’ as its elements.

Solution for Java 8. A bit longer than the Guava one, but at least you don't have to install a library.

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

//...

List<Integer> integers = Arrays.asList(1, 2, 3, 4);
List<String> strings = integers.stream().map(Object::toString)
                                        .collect(Collectors.toList());

Python tips, There are a few useful tips to convert a Python list (or any other iterable such as a tuple) to a string for display. First, if it is a list of strings, you may simply use join  numList = [20, 213, 4587, 7869] print (str (numList).strip (' []')) The output is as follows: 20, 213, 4587, 7869. Alternatively, we can use map () function to convert the items in the list to a string. After that, we can join them as below: print (', '.join (map (str, numList))) The output: 20, 213, 4587, 7869.

What you're doing is fine, but if you feel the need to 'Java-it-up' you could use a Transformer and the collect method from Apache Commons, e.g.:

public class IntegerToStringTransformer implements Transformer<Integer, String> {
   public String transform(final Integer i) {
      return (i == null ? null : i.toString());
   }
}

..and then..

CollectionUtils.collect(
   collectionOfIntegers, 
   new IntegerToStringTransformer(), 
   newCollectionOfStrings);

How to convert list to string, By using ''.join list1 = ['1', '2', '3'] str1 = ''.join(list1). Or if the list is of integers, convert the elements before joining them. list1 = [1, 2, 3] str1  import json. # initializing string representation of a list. ini_list = " [1, 2, 3, 4, 5]" # printing intialized string of list and its type. print ("initial string", ini_list) print (type(ini_list)) # Converting string to list. res = json.loads (ini_list) # printing final result and its type.

The source for String.valueOf shows this:

public static String valueOf(Object obj) {
    return (obj == null) ? "null" : obj.toString();
}

Not that it matters much, but I would use toString.

How to Convert Python List to String with Examples, While programming, you may face many scenarios where list to string conversion is required. Let's now see how can we use the join() method in such different  How to convert list into excel? Ask Question Asked 2 years, 6 months ago. Converting string into datetime. 3415. How to make a flat list out of list of lists?

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Convert list to string in python using join() / reduce() / map , Convert list to string by join all the strings items in the list to create a concatenated string,. def convert_list_to_string(org_list, seperator=  Thus, for each conversion, you will use multiplication as you’re going from larger to smaller. Here are your conversions: 6 d x 24 hr = 144 hr 144 hr x 60 min = 8640 min 16 hr x 60 min = 960 min 8640 min + 960 min + 34 min = 9634 min In the first conversion, we used 24 hours because there are 24 hours in a day.

How to convert a list to an array in Python, Lists can be converted to arrays using the built-in functions in the Python numpy library. numpy provides us with two functions to use when converting a list into an​  In Python lists can be converted to arrays by using two methods from the NumPy library: The vital difference between the above two methods is that numpy.array () will make a duplicate of the original object and numpy.asarray () would mirror the changes in the original object.

Comments
  • When It is simple, this is called beauty.
  • The original poster seemed to indicate that he had thought of this but considered this solution too complex or tedious. But I'm hard-pressed to imagine what could be easier. Yes, sometimes you have to write 3 or 4 lines of code to get a job done.
  • But that binds you to ArrayList. Can this be done using the same implementation as the original list?
  • @Andreas oldList.getClass().newInstance() will do
  • It will be nice if there are more ready functions beside Functions.toStringFunction()
  • clean but maybe not as fast.. 1 extra function call per value ?
  • HotSpot can inline function calls - so if it's called enough, it shouldn't make a difference.
  • I don't downvote this because it is indeed a solution. But encouraging people to add a library dependency to solve such simple task is a no-go for me.
  • Nice solution if you are already using Guava in our solution.
  • While this is a bit longer for the toString example, it ends up being shorter for conversions not supported by Guava's Functions library. Custom Functions are still easy, but it is significantly more code then this Java 8 stream
  • CollectionUtils.collect(collectionOfIntegers, new org.apache.commons.collections.functors.StringValueTransformer()); But , StringValueTransformer uses the String.valueOf ...
  • Unless new work has been done on apache collections, they don't do generics.
  • This is really Java-ing-it down. This is not idiomatic Java, and more like functional programming. Maybe when we get closures in Java 8 could you call it idiomatic Java.
  • You definitely want to use Collections4 for that (not the old 3.x Collections) for support of generics: commons.apache.org/proper/commons-collections/apidocs/org/…