Array Constructor References
Description
We can create an array using array constructor as follows.
ArrayTypeName::new
int[]::new is calling new int[].
new int[] requires an int type value as the array
length, therefore the int[]::new needs
an int type input value.
Example
The following code uses the array constructor reference to create an int array.
import java.util.Arrays;
import java.util.function.IntFunction;
/*from ww w. ja v a 2s . c o m*/
public class Main{
public static void main(String[] argv){
IntFunction<int[]> arrayCreator1 = size -> new int[size];
// Creates an int array of five elements
int[] intArray1 = arrayCreator1.apply(5);
System.out.println(Arrays.toString(intArray1));
IntFunction<int[]> arrayCreator2 = int[]::new;
int[] intArray2 = arrayCreator2.apply(5);
System.out.println(Arrays.toString(intArray2));
}
}
The code above generates the following result.
Example 2
By using Function<Integer,ArrayType> we can specify
array type in the declaration.
import java.util.Arrays;
import java.util.function.Function;
/*w ww . ja v a2s . com*/
public class Main{
public static void main(String[] argv){
Function<Integer,int[]> arrayCreator3 = int[]::new;
int[] intArray = arrayCreator3.apply(5);
System.out.println(Arrays.toString(intArray));
}
}
The code above generates the following result.
Example 3
We can specify the length for the first dimension when creating a two-dimensional array.
import java.util.Arrays;
import java.util.function.IntFunction;
//from w w w . j av a 2s. co m
public class Main{
public static void main(String[] argv){
IntFunction<int[][]> TwoDimArrayCreator = int[][]::new;
int[][] intArray = TwoDimArrayCreator.apply(5);
// Creates an int[5][] array
intArray[0] = new int[5];
intArray[1] = new int[5];
intArray[2] = new int[5];
intArray[3] = new int[5];
intArray[4] = new int[5];
System.out.println(Arrays.deepToString(intArray));
}
}
The code above generates the following result.
