Java multidimensional Array to string and String to Array

Question

I have array

data[][];

convert to string:

string = Arrays.deepToString(data);

string:

[[1, 1394119227787, 59474093, USD/DKK, true, 0.05, 5.391582, 5.00663, 5.39663, null, null], [1, 1394581174413, 59500543, EUR/JPY, false, 0.05, 142.489381, 145.3, 139.68, null, null],
[1, 1394581174413, 59500543, EUR/JPY, false, 0.05, 142.489381, 145.3, 139.68, null, null],
[1, 1394581174413, 59500543, EUR/JPY, false, 0.05, 142.489381, 145.3, 139.68, null, null]]

and How convert this string back to array?

You can't do that; there is no bijection between objects and string representations. — fge
– fge, Commented Mar 13, 2014 at 11:48
@MarounMaroun I assume that the original array is no longer available. — Pablo
– Pablo, Commented Mar 13, 2014 at 11:48
How convert multidimensional array to string and back to array — zix
– zix, Commented Mar 13, 2014 at 11:50
I ned convert array to string send via https to sever www(php file) and recive string back and then convert to array — zix
– zix, Commented Mar 13, 2014 at 11:50

Akhilesh Dhar Dubey · Accepted Answer · 2014-03-15 19:51:24Z

Try my stringToDeep() method to convert back to Array.

import java.util.*;

public class DeepToArray {

public static void main(String[] args) {

    int row, col;
    row = 2;
    col = 3;
    String[][] in = new String[row][col];

    for (int i = 0; i < row; i++) {
        for (int j = 0; j < col; j++) {
            in[i][j] = i + " " + j;
        }
    }
    String str = Arrays.deepToString(in);

    System.out.println(str);

    String[][] out = stringToDeep(str);

    for (String s2[] : out) {
        for (String s3 : s2) {
            System.out.print(s3 + "  ");
        }
        System.out.println();
    }
}

private static String[][] stringToDeep(String str) {
    int row = 0;
    int col = 0;
    for (int i = 0; i < str.length(); i++) {
        if (str.charAt(i) == '[') {
            row++;
        }
    }
    row--;
    for (int i = 0;; i++) {
        if (str.charAt(i) == ',') {
            col++;
        }
        if (str.charAt(i) == ']') {
            break;
        }
    }
    col++;

    String[][] out = new String[row][col];

    str = str.replaceAll("\\[", "").replaceAll("\\]", "");

    String[] s1 = str.split(", ");

    int j = -1;
    for (int i = 0; i < s1.length; i++) {
        if (i % col == 0) {
            j++;
        }
        out[j][i % col] = s1[i];
        //System.out.println(s1[i] + "\t" + j + "\t" + i % col);
    }
    return out;
}
}

Ernest Friedman-Hill · Accepted Answer · 2014-03-13 11:47:29Z

4

There is no method in the java API that will automatically convert this back to an array. You could write code to do this yourself, but it would be tricky; this format does not escape special characters like the square brackets, or the commas. It might be easier just to use a format which is designed for encoding and decoding arrays, like JSON.

answered Mar 13, 2014 at 11:47

Ernest Friedman-Hill

81.9k11 gold badges158 silver badges191 bronze badges

4 Comments

zix Over a year ago

maybe simple example?

Pablo Over a year ago

@zix The answer is basically "don't do this". You are inventing your own way of serializing data, instead of using a standard way, like for example JSON.

JDGuide Over a year ago

How to convert the string back to array ?

zix Over a year ago

int i = 0; int j = 0; String string = ""; for(j = 0; j<10; j++){ for(i = 0; i<10; i++){ string += data[j][i] + "#"; } string += "$$"; }

Ti Strga · Accepted Answer · 2020-08-22 04:22:10Z

All the answers I found are 2-dimensional only, so here's my solution to reverse deepToString(...) for any number of dimensions:

Usage example:

String arrString = "[[[0.11695497071135137, 0.8830064157596283, 0.3433854446148375, 0.18825445694298526, 1.0441938749175883, 0.8941633746325311], [-0.089908138214512, 0.39821330927870574, 0.1365997500579524, 0.7008902956765364, 0.9897596683277262, 0.2847717055995359], [0.6450670283688857, 0.01516064860567864, -0.07904927386204857, 0.2703900981351612, 0.45402985012492075, 0.30505608337251183], [0.5122943117220898, 0.008726346575469023, 0.7734611917871235, 0.3051772999891666, 0.5237487372571624, 1.1824105144656751]]]";
String[][][] arr = (String[][][]) reverseDeepToString(arrString);
System.out.println(Arrays.deepToString(arr));

This code converts a string (arrString) into an array, and then the function Arrays.deepToString(...) converts it back into the same string.

Function code:

public static Object reverseDeepToString(String str){
    int dimensions = 0;
    for(int x = 0; x < str.length(); x++)
        if(str.charAt(x) == '[')
            dimensions++;
        else break;
    str = str.substring(dimensions, str.length() - dimensions);
    return createArrayRecursive(str, dimensions);
}

private static Object createArrayRecursive(String str, int dimension){
    
    if(dimension == 1)
        return str.split(", "); // modify the code here if you want to convert the strings to another variable type
    
    String[] s = str.split(getArraySeparator(dimension));
    int[] lengths = new int[dimension];
    lengths[0] = s.length;
    Object arr = Array.newInstance(String.class, lengths); // and here (see comment above)
    
    for(int x = 0; x < s.length; x++)
        Array.set(arr, x, createArrayRecursive(s[x], dimension - 1));
    
    return arr;
}

private static String getArraySeparator(int dimension){
    String separator = ", ";
    for(int x = 1; x < dimension; x++)
        separator = ']' + separator + "\\[";
    return separator;
}

zix · Accepted Answer · 2014-03-15 17:05:03Z

Array to string and back to array :P

import java.util.Arrays;
import java.util.Random;

public class arrays {

    public static void main(String [ ] args)
    {
        String[][] in = new String [10][4];
        String[][] out = new String [10][4];
        arrays nr = new arrays();

        for(int i =0; i< 4; i++){
            for(int j =0; j< 4; j++){
                in[i][j] = nr.Rand(5);
            }       
        }
        System.out.println(Arrays.deepToString(in));

        // tablica ok
        // convert array to string
        String line = "";
        for(int i =0; i< 4; i++){
            for(int j =0; j< 4; j++){
                line += in[i][j] + "_";
            }       
            line += ":";
        }

        System.out.println(line);

        // line back to array

         String[] xline = line.split(":");

         int ss = 0;
         for (String str : xline) {
             out[ss] = (String[]) str.split("_");

              System.out.println("string line>>>" + str);

              ss++;
         }

         System.out.println(Arrays.deepToString(out));
    }

      public String nextSessionId() {
          //private SecureRandom random = new SecureRandom();
          //return new BigInteger(130, random).toString(32);
          return null;
      }

      public String Rand(int zz){
          char[] chars = "987654321abcdefghijklm111nopqrstuvwxyz0123456789".toCharArray();
          StringBuilder sb = new StringBuilder();
          Random random = new Random();
          for (int i = 0; i < zz; i++) {
              char c = chars[random.nextInt(chars.length)];
              sb.append(c);
          }
          String output = sb.toString();
          //    System.out.println(output);
          return output;

      }
}

:D

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