In this tutorial we will learn how to convert Array to List and how to convert ArrayList to array in Java with example and programs.
How to convert Array to List >
- Program/Example 1.1 to convert String Array to List in java>
- Program/Example 1.2 to convert Integer Array to List in java >
- Also, we will create program to convert String Array to Collection in java >
How to convert ArrayList to array in Java >
- Program/Example 2.1 to convert ArrayList to String array in java>
- Program/Example 2.2 to convert ArrayList to Integer array in java >
How to convert Array to List >
Program/Example 1.1 to convert String Array to List in java>
java.util.Arrays.asList method returns fixed size list, i.e. unmodifiable list
import java.util.Arrays;
import java.util.List;
public class ConvertStringArrayToListExample {
public static void main(String[] args) {
String stringArray[] = { "a", "b" };
//convert Array to List
List<String> list = Arrays.asList(stringArray);
//Display
System.out.println(list);
}
}
/*OUTPUT
[a, b]
*/
|
java.util.Arrays.asList method returns fixed size list, i.e. unmodifiable list and Modifying unmodifiable list either by adding or removing elements throws UnsupportedOperationException in java. The list returned is serializable and implements RandomAccess interface. RandomAccess is a(Marker interface) which indicate that list supports fast random access (i.e. index based access)
Program/Example 1.2 to convert Integer Array to List in java >
import java.util.Arrays;
import java.util.List;
public class ConvertIntegerArrayToListExample {
public static void main(String[] args) {
Integer integerArray[] = { 1, 2 };
// convert Array to List
List<Integer> list = Arrays.asList(integerArray);
// Display list
System.out.println(list);
}
}
/*OUTPUT
[1, 2]
*/
|
So far in this tutorial we learned how to convert Array to List and now we will learn how to convert ArrayList to array in Java with example and programs.
How to convert ArrayList to array in Java >
Program/Example 2.1 to convert ArrayList to String array in java>
import java.util.ArrayList;
import java.util.List;
public class ConvertArrayListToStringArrayExample {
public static void main(String[] args) {
List<String> arrayList = new ArrayList<String>();
arrayList.add("a");
arrayList.add("b");
//Create stringArray of ArrayList's size
String[] stringArray = new String[arrayList.size()];
//Use toArray method to convert ArrayList to Array
arrayList.toArray(stringArray);
//Let's display the stringArray
System.out.println("Display the stringArray");
for(int i=0; i<stringArray.length; i++){
System.out.print(stringArray[i]+" ");
}
}
}
/*OUTPUT
Display the stringArray
a b
*/
|
toArray method returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list.
Program/Example 2.2 to convert ArrayList to Integer array in java >
import java.util.ArrayList;
import java.util.List;
public class ConvertArrayListToIntegerArrayExample {
public static void main(String[] args) {
List<Integer> arrayList = new ArrayList<Integer>();
arrayList.add(1);
arrayList.add(2);
//Create integerArray of ArrayList's size
Integer[] integerArray = new Integer[arrayList.size()];
//Use toArray method to convert ArrayList to Array
arrayList.toArray(integerArray);
//Let's display the integerArray
System.out.println("Display the integerArray");
for(int i=0; i<integerArray.length; i++){
System.out.print(integerArray[i]+" ");
}
}
}
/*OUTPUT
Display the integerArray
1 2
*/
|
Program/Example to convert String Array to Collection in java >
Collection is super interface of List interface, so Arrays.asList(stringArray) can be referred by reference variable of type java.util.List or java.util.Collection
import java.util.Arrays;
import java.util.Collection;
public class ConvertArrayToCollectionExample {
public static void main(String[] args) {
String stringArray[] = {"a", "b"};
//convert Array to Collection
Collection<String> collection = Arrays.asList(stringArray);
//Display Collection
System.out.println(collection);
}
}
/*OUTPUT
[a, b]
*/
|
So, In this tutorial we learned how to convert Array to List and how to convert ArrayList to array in Java with example and programs.
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