I have the situation where I need to build a arrayC[] in Java from a arrayA[4] and a arrayB[7] , where arrayC[] must display arrayA[4] and then arrayB[7] :
For example:
arrayA[4] = {A0; A1; A2; A3};
arrayB[7] = {B0; B1; B2; B3; B4; B5; B6};
arrayC[i] = {A0; A1; A2; A3; B0; B1; B2; B3; B4; B5; B6};
How can I do this?
There are numerous ways to do this. One way is this:
XXX[] arrayC = new XXX[arrayA.length + arrayB.length];
for (int i = 0; i < arrayA.length; i++) {
arrayC[i] = arrayA[i];
}
for (int i = 0; i < arrayB.length; i++) {
arrayC[i + arrayA.length] = arrayB[i];
}
In the example above, XXX[] is the type of the array. This can be int[] , boolean[] , String[] , Object[] , etc.
Another way:
XXX[] arrayC = new XXX[arrayA.length + arrayB.length];
System.arraycopy(arrayA, 0, arrayC, 0, arrayA.length);
System.arraycopy(arrayB, 0, arrayC, arrayA.length, arrayB.length);
A third form, if the base type of the array is not a primitive type:
List<XXX> lista = new ArrayList<>();
lista.addAll(Arrays.asList(arrayA));
lista.addAll(Arrays.asList(arrayB));
XXX[] arrayC = lista.toArray(new XXX[0]);
A fourth form, using Stream s:
XXX[] arrayC = Stream.concat(Stream.of(arrayA), Stream.of(arrayB)).toArray(XXX[]::new);
In Java 8 onwards:
import java.util.*;
import java.util.stream.*;
public class HelloWorld{
public static void main(String []args){
int[] a = new int[] { 1, 2, 3 };
int[] b = new int[] { 40, 50, 60 };
int[] array =
IntStream.concat(Arrays.stream(a), Arrays.stream(b))
.toArray();
System.out.println(Arrays.toString(array));
}
}