Arraylist to String

Question

Given an ArrayList of ArrayList of Bytes like this :

 ArrayList<ArrayList<Byte> > shares = new ArrayList<ArrayList<Byte> >();

I want to convert this to an array of String which is defined like this :

String[] binary=new String[shares.size()];

How to do it.Please help

How to do reverse of it also.Means how to convert this string back to arraylist.

Check this answer hope it will help you http://stackoverflow.com/questions/9572795/convert-list-to-array-in-java — Sergey Pekar, Mar 17 '14 at 10:36
Most basic approach would be iterate over outer list and for each outer iteration iterate on the inner list and put it in the array. Time complexity --> **O(N^2)** — Aniket Thakur, Mar 17 '14 at 10:37

score 0 · Answer 1 · edited May 23 '17 at 12:32

0

Check toArray method of ArrayList Also you can find simmilar question here

edited May 23 '17 at 12:32

Community

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answered Mar 17 '14 at 10:38

Sergey Pekar

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morpheus05 · Answer 2 · 2014-03-17T10:52:06.997

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Iterate over the outer list and convert every entry to a string.

e.g.

ArrayList<String> result = new ArrayList<>(shares.size());
for(ArrayList<Byte> bytes: shares) {
   result.add(bytes.toString());
}

If you want the result as a string array you can do it this way:

String[] result = new String[shares.size()];
for(int i = 0; i < result.length; ++i) {
   ArrayList<Byte> bytes = shares.get(i);
   result[i] = bytes.toString();
}

If the bytes actually represent a string (you want the characters and not the bytes as numbers printed) then you would have to convert the inner list to an array (see other answers) and instantiate a string with it. If you want the encoding stuff see Java - String getBytes()

edited Mar 17 '14 at 10:52

answered Mar 17 '14 at 10:40

morpheus05

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What about revrse of it ? – user3425204 Mar 17 '14 at 10:45
it depends what you wanna do: Strings with the bytes as numbers or the actual characters. In one case you would have to parse it in the other convert it with the String ctor and getBytes() method - attention encoding! – morpheus05 Mar 17 '14 at 10:49
firstly i think in your code instead of result.length it should be result.size() . secondly string has nly numbers – user3425204 Mar 17 '14 at 10:51
result is an array in the second case so it has to be length. I don't understand your second point... ? – morpheus05 Mar 17 '14 at 10:53
you means its equal to shares.size() naa? – user3425204 Mar 17 '14 at 10:57
Yes the value is identical – morpheus05 Mar 17 '14 at 11:07

score 0 · Answer 3 · answered Mar 17 '14 at 11:08

Have a look at this will help-

  public static void main(String[] args) {
    ArrayList<ArrayList<Byte>> shares = new ArrayList<ArrayList<Byte>>(0);
    ArrayList<Byte> b = new ArrayList<Byte>();
    b.add(new Byte("0"));
    b.add(new Byte("1"));

    shares.add(b);

    Byte[] b1 = new Byte[shares.size()];
    b1 = shares.get(0).toArray(b1);
    System.out.println(Arrays.toString(b1));

}

Arraylist to String

3 Answers3