Converting a list between different data types

Question

What will be the easiest way to convert List<Integer> to List<String> objects. I am currently repeating all integers and adding them to List<String> objects , is there already a useful function?

Answer 1

You have found an easy way. The type is "incompatible", so you need a conversion rule (which is simple in your case). The algorithm will always be O (n), regardless of iterating through the collections manually or calling some API method from some third-party library (the JRE does not offer an API for your task).

Answer 2

Although there are some libraries that can perform general List conversions (e.g. Google Guava ) using one for this case, probably t will save you any lines of code, since you need to create a Function object, and this in itself includes many templates that your existing code is probably smaller.

Answer 3

I don’t think there is an automatic way to do this, simply because of how Java compiles common arguments (called type erasure, a difficult way to say “Haha, we actually only save object references and the compiler inserts the cast into the general argument each time you do get () ").

Why should you convert it to a list of strings? Isn't it the same when you need a list of strings to just iterate over a list of integers and call toString () on each of them?

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EDIT:

anyway, here is a solution that will work:

 public static List<String> convToString(List<Integer> list){ List<String> ret = new ArrayList<String>(); for (Integer i : list){ ret.add(i.toString()); } return ret; } 

And again!

 public static List<Integer> convToInteger(List<String> list){ List<Integer> ret = new ArrayList<Integer>(); for (String s : list){ ret.add(Integer.parseInt(s)); } return ret; } 

Answer 4

I do not think we have a utility function for this task. Even for this, there is a utility function, you may need to iterate through List<Integer>

Answer 5

Do I need to have a list structure? Why not make Map<Integer, String> , and when an integer is inserted, the String value of that integer can be created.