Converting ArrayList to Array in java

Question

I have an ArrayList with values like "abcd#xyz" and "mnop#qrs". I want to convert it into an Array and then split it with # as delimiter and have abcd,mnop in an array and xyz,qrs in another array. I tried the following code:

String dsf[] = new String[al.size()]; 
for(int i =0;i<al.size();i++){
 dsf[i] = al.get(i);
}

But it failed saying "Ljava.lang.String;@57ba57ba"

• Guillaume Polet: POst the definition of your ArrayList and the complete error message
• Jon Skeet: What do you mean by "it failed saying ..."? That looks like the result of printing dsf.toString()...
• Adam: Do you want an array of arrays of Strings, i.e. a 2 dimensional array?
• Nateowami: possible duplicate of Convert ArrayList containing Strings to an array of Strings in Java?

Answer 1

You don't need to reinvent the wheel, here's the toArray() method:

String []dsf = new String[al.size()];
al.toArray(dsf);

• Shruthi: ArrayList<String> a1 = new ArrayList<String>(); for (Entry<String, String> entry : outmap.entrySet()) { if(entry.getKey().indexOf("Data") != -1){ exports.add(entry.getValue()); } }
• wmorrison365: There's also this form 'docs.oracle.com/javase/1.5.0/docs/api/java/util/…' for where you want to provide a specificly typed array.

Answer 2

List<String> list=new ArrayList<String>();
list.add("sravan");
list.add("vasu");
list.add("raki");
String names[]=list.toArray(new String[list.size()])

Answer 3

List<String> list=new ArrayList<String>();
list.add("sravan");
list.add("vasu");
list.add("raki"); 
String names[]=list.toArray(new String[0]);

if you see the last line (new String[0]), you don't have to give the size, there are time when we don't know the length of the list, so to start with giving it as 0 , the constructed array will resize.

• ישו אוהב אותך: I think new String[0] redundant because you always have the list. So you can determine the size.
• ᴛʜᴇᴘᴀᴛᴇʟ: You can/should replace new String[0] with new String[list.size()]

Answer 4

import java.util.*;
public class arrayList {
 public static void main(String[] args) {
 Scanner sc=new Scanner(System.in);
 ArrayList<String > x=new ArrayList<>();
 //inserting element
 x.add(sc.next());
 x.add(sc.next());
 x.add(sc.next());
 x.add(sc.next());
 x.add(sc.next());
 //to show element
 System.out.println(x);
 //converting arraylist to stringarray
 String[]a=x.toArray(new String[x.size()]);
 for(String s:a)
 System.out.print(s+" ");
 }
}

• rghome: This doesn't do the requested split.
• insomniac: provide description for an answer if you want others to understand and maybe upvote it
• Bernhard Barker: This approach is the same as the one in this answer posted a few years earlier.

Answer 5

String[] values = new String[arrayList.size()];
 for (int i = 0; i < arrayList.size(); i++) {
 values[i] = arrayList.get(i).type;
 }

• Anand: Here arrayList.get(i).type is a one of the value in the arrayList. You can get it anyway.

Answer 6

What you did with the iteration is not wrong from what I can make of it based on the question. It gives you a valid array of String objects. Like mentioned in another answer it is however easier to use the toArray() method available for the ArrayList object => http://docs.oracle.com/javase/1.5.0/docs/api/java/util/ArrayList.html#toArray%28%29

Just a side note. If you would iterate your dsf array properly and print each element on its own you would get valid output. Like this:

for(String str : dsf){
 System.out.println(str);
}

What you probably tried to do was print the complete Array object at once since that would give an object memory address like you got in your question. If you see that kind of output you need to provide a toString() method for the object you're printing.

Answer 7

package com.v4common.shared.beans.audittrail;
import java.util.ArrayList;
import java.util.List;
public class test1 {
 public static void main(String arg[]){
 List<String> list = new ArrayList<String>();
 list.add("abcd#xyz");
 list.add("mnop#qrs");
 Object[] s = list.toArray();
 String[] s1= new String[list.size()];
 String[] s2= new String[list.size()];
 for(int i=0;i<s.length;i++){
 if(s[i] instanceof String){
 String temp = (String)s[i];
 if(temp.contains("#")){
 String[] tempString = temp.split("#");
 for(int j=0;j<tempString.length;j++) {
 s1[i] = tempString[0];
 s2[i] = tempString[1];
 }
 }
 } 
 }
 System.out.println(s1.length);
 System.out.println(s2.length);
 System.out.println(s1[0]);
 System.out.println(s1[1]);
 }
}

Answer 8

Here is the solution for you given scenario -

List<String>ls = new ArrayList<String>();
 ls.add("dfsa#FSDfsd");
 ls.add("dfsdaor#ooiui");
 String[] firstArray = new String[ls.size()]; 
 firstArray =ls.toArray(firstArray);
String[] secondArray = new String[ls.size()];
for(int i=0;i<ls.size();i++){
secondArray[i]=firstArray[i].split("#")[0];
firstArray[i]=firstArray[i].split("#")[1];
} 

Answer 9

This is the right answer you want and this solution i have run my self on netbeans

ArrayList a=new ArrayList();
a.add(1);
a.add(3);
a.add(4);
a.add(5);
a.add(8);
a.add(12);
int b[]= new int [6];
 Integer m[] = new Integer[a.size()];//***Very important conversion to array*****
 m=(Integer[]) a.toArray(m);
for(int i=0;i<a.size();i++)
{
 b[i]=m[i]; 
 System.out.println(b[i]);
} 
 System.out.println(a.size());

• Tom: How is your answer better when the existing one and now only worse due to the use of raw-types?

Answer 10

NameOfArray.toArray(new String[0])

This will convert ArrayList to Array in java

Answer 11

This can be done using stream:

List<String> stringList = Arrays.asList("abc#bcd", "mno#pqr");
 List<String[]> objects = stringList.stream()
 .map(s -> s.split("#"))
 .collect(Collectors.toList());

The return value would be arrays of split string. This avoids converting the arraylist to an array and performing the operation.

Answer 12

// A Java program to convert an ArrayList to arr[]
import java.io.*;
import java.util.List;
import java.util.ArrayList;
class Main {
 public static void main(String[] args)
 {
 List<Integer> al = new ArrayList<Integer>();
 al.add(10);
 al.add(20);
 al.add(30);
 al.add(40);
 Integer[] arr = new Integer[al.size()];
 arr = al.toArray(arr);
 for (Integer x : arr)
 System.out.print(x + " ");
 }
 }

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