I have a problem in converting from Array to ArrayList
public class one
{
public static void main(String args[])
{
int y[]={12,25,38,46};
two p=new two();
p.setLocations(y);
}
}
import java.io.*;
import java.util.*;
public class two
{
ArrayList<Integer> data_array=new ArrayList<Integer>();
void setLocations(int locations[])
{
ArrayList<Integer> locations_arraylist=new ArrayList(Arrays.asList(locations));
data_array=locations_arraylist;
for(int i=0;i<data_array.size();i++)
System.out.println("data_array["+i+"]="+data_array.get(i));
}
}
In the below line
ArrayList<Integer> locations_arraylist=new ArrayList(Arrays.asList(locations));
//Copying from array to ArrayList-Its converting,Please suggest
An int[]
is quite different from a List<Integer>
. For example, an Integer
has an identity as well as a value. There is no very simple way to do the conversion.
The following way works with Java 8.
int[] array = {1, 2, 3, 4, 5};
List<Integer> list = IntStream.of(array).boxed().collect(Collectors.toCollection(ArrayList::new));
The following way works in earlier versions.
int[] array = {1, 2, 3, 4, 5};
List<Integer> list = new ArrayList<Integer>();
for (int a : array)
list.add(a);
If you pass an int[]
to Arrays.asList
you get a List<int[]>
, not a List<Integer>
.
It is recommended to use the interface List
for members/variables and use the ArrayList
constructor. Also ArrayList
without the brackets indicates the raw type instead of instead of the generic.
If you would like to avoid a for loop that will copy the values from array to List
, there are 2 solutions :
Guava (put on top import com.google.common.primitives.Ints;
)
List<Integer> locations_arraylist = Ints.asList(locations);
pass the values to Arrays.asList()
directly
List<Integer> locations_arraylist = Arrays.asList(12, 25, 38, 46);
You can try this:
replace int y[]={12,25,38,46};
to Integer y[] = {12, 25, 38, 46};
No need of this line as well
ArrayList<Integer> data_array = new ArrayList<Integer>();
You can use for-each loop for print the array :
int i=0;
for (Integer locations_arraylist1 : locations_arraylist) {
System.out.println("data_array[" + i + "]=" + locations_arraylist1);
i++;
}
Try this:
int[] arrayInt = new int[]{1, 2, 3};
List<Integer> list = Arrays.asList(ArrayUtils.toObject(arrayInt));
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