Java - Comment rejoindre des tableaux
Dans cet article, nous allons vous montrer quelques façons de rejoindre un tableau Java.
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Apache Commons Lang - ArrayUtils
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API Java
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Flux Java 8
1. Apache Commons Lang - ArrayUtils
Le moyen le plus simple est d'ajouter la bibliothèqueApache Commons Lang et d'utiliserArrayUtils. addAll pour joindre les tableaux. Cette méthode prend en charge les tableaux de type primitif et objet.
JoinArray.java
package com.example.example.array;
import org.apache.commons.lang3.ArrayUtils;
import java.util.Arrays;
public class JoinArray {
public static void main(String[] args) {
String[] s1 = new String[]{"a", "b", "c"};
String[] s2 = new String[]{"d", "e", "f"};
String[] result = ArrayUtils.addAll(s1, s2);
System.out.println(Arrays.toString(result));
int [] int1 = new int[]{1,2,3};
int[] int2 = new int[]{4,5,6};
int[] result2 = ArrayUtils.addAll(int1, int2);
System.out.println(Arrays.toString(result2));
}
}
Sortie
[a, b, c, d, e, f] [1, 2, 3, 4, 5, 6]
Pour l'utilisateur Maven.
pom.xml
org.apache.commons commons-lang3 3.4
2. API Java
Exemple d'API Java pur, prend en charge les types primitifs et génériques.
JoinArray.java
package com.example.example.array;
import java.lang.reflect.Array;
import java.util.Arrays;
public class JoinArray {
public static void main(String[] args) {
String[] s1 = new String[]{"a", "b", "c"};
String[] s2 = new String[]{"d", "e", "f"};
String[] s3 = new String[]{"g", "h", "i"};
String[] result = joinArrayGeneric(s1, s2, s3);
System.out.println(Arrays.toString(result));
int[] int1 = new int[]{1, 2, 3};
int[] int2 = new int[]{4, 5, 6};
int[] int3 = new int[]{7, 8, 9};
int[] result2 = joinArray(int1, int2, int3);
System.out.println(Arrays.toString(result2));
}
static T[] joinArrayGeneric(T[]... arrays) {
int length = 0;
for (T[] array : arrays) {
length += array.length;
}
//T[] result = new T[length];
final T[] result = (T[]) Array.newInstance(arrays[0].getClass().getComponentType(), length);
int offset = 0;
for (T[] array : arrays) {
System.arraycopy(array, 0, result, offset, array.length);
offset += array.length;
}
return result;
}
static int[] joinArray(int[]... arrays) {
int length = 0;
for (int[] array : arrays) {
length += array.length;
}
final int[] result = new int[length];
int offset = 0;
for (int[] array : arrays) {
System.arraycopy(array, 0, result, offset, array.length);
offset += array.length;
}
return result;
}
//create other overloaded primitive type - long, double...
//static long[] joinArray(long[]... arrays)
}
Sortie
[a, b, c, d, e, f, g, h, i] [1, 2, 3, 4, 5, 6, 7, 8, 9]
3. Flux Java 8
Exemple de flux Java 8 pour joindre des tableaux.
JoinArray.java
package com.example.example.array;
import java.util.Arrays;
import java.util.stream.IntStream;
import java.util.stream.Stream;
public class JoinArray {
public static void main(String[] args) {
String[] s1 = new String[]{"a", "b", "c"};
String[] s2 = new String[]{"d", "e", "f"};
String[] s3 = new String[]{"g", "h", "i"};
//join object type array
String[] result = Stream.of(s1, s2, s3).flatMap(Stream::of).toArray(String[]::new);
System.out.println(Arrays.toString(result));
int [] int1 = new int[]{1,2,3};
int[] int2 = new int[]{4,5,6};
int[] int3 = new int[]{7,8,9};
//join 2 primitive type array
int[] result2 = IntStream.concat(Arrays.stream(int1), Arrays.stream(int2)).toArray();
//join 3 primitive type array, any better idea?
int[] result3 = IntStream.concat(Arrays.stream(int1),
IntStream.concat(Arrays.stream(int2), Arrays.stream(int3))).toArray();
System.out.println(Arrays.toString(result2));
System.out.println(Arrays.toString(result3));
}
}
Sortie
[a, b, c, d, e, f, g, h, i] [1, 2, 3, 4, 5, 6] [1, 2, 3, 4, 5, 6, 7, 8, 9]
Un meilleur exemple de flux Java 8? Faites un commentaire ci-dessous.