En Java, comment rejoindre Arrays ? 3 façons : Apache Commons ArrayUtils, Java 8 Streams et Simple APIs

Publié: 2022-01-20
En Java, comment rejoindre Arrays ? 3 façons - Apache Commons ArrayUtils, Java 8 Streams et API simples

Dans ce didacticiel, nous allons passer en revue différentes manières de joindre des tableaux Java.

Si vous avez l'une des questions ci-dessous, vous êtes au bon endroit :

  • Comment concaténer deux tableaux en Java ?
  • Comment fusionner deux tableaux en Java ?
  • 3 façons de combiner des tableaux en Java
  • Joindre un tableau de primitives avec un séparateur en Java

Voici les trois façons dont vous pouvez joindre des tableaux en Java.

  1. Join Array à l'aide de l'utilitaire Apache Common
  2. Join Array à l'aide de l'opération Java8 Stream
  3. Rejoindre Array à l'aide des API Java standard

Commençons:

Créez la classe Java CrunchifyJoinArrays3Ways.java .

Mettez le code Java ci-dessous dans le fichier.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
package crunchify . com . tutorial ;
 
import org . apache . commons . lang3 . ArrayUtils ;
 
import java . lang . reflect . Array ;
import java . util . Arrays ;
import java . util . stream . IntStream ;
import java . util . stream . Stream ;
 
/**
* @author Crunchify.com
* <p>
* In Java how to join Arrays? 3 ways: Apache Commons ArrayUtils, Java 8 Streams and Simple APIs.
* Version: 1.0.3
*/
public class CrunchifyJoinArrays3Ways {
     public static void main ( String [ ] args ) {
 
         crunchifyPrint ( "Original String Array1: [google, twitter]" ) ;
         crunchifyPrint ( "Original String Array2: [apple, microsoft]" ) ;
         crunchifyPrint ( "Original Integer Array1: [111, 444]" ) ;
         crunchifyPrint ( "Original Integer Array2: [222, 555]\n" ) ;
         // Join Array using Apache Common utility
         joinArrayUsingApacheCommon ( ) ;
 
         // Join Array using Java8 Stream operation
         joinArrayUsingJava8Stream ( ) ;
 
         // Join Array using Standard Java APIs
         joinArrayUsingJavaAPI ( ) ;
     }
 
     // Method-1: Join Array using Apache Common utility
     private static void joinArrayUsingApacheCommon ( ) {
 
         String [ ] company1 = new String [ ] { "google" , "twitter" } ;
         String [ ] company2 = new String [ ] { "apple" , "microsoft" } ;
 
         // from org.apache.commons.lang3 maven dependency
         String [ ] crunchifyResult = ArrayUtils . addAll ( company1 , company2 ) ;
 
         crunchifyPrint ( "From Method-1: addAll() - String ==> " + Arrays . toString ( crunchifyResult ) ) ;
 
         int [ ] crunchifyArray1 = new int [ ] { 111 , 444 } ;
         int [ ] crunchifyArray2 = new int [ ] { 222 , 555 } ;
 
         int [ ] crunchifyResult2 = ArrayUtils . addAll ( crunchifyArray1 , crunchifyArray2 ) ;
 
         crunchifyPrint ( "From Method-1: addAll() - Integer ==> " + Arrays . toString ( crunchifyResult2 ) ) ;
     }
 
     // Simple Java Print Method
     private static void crunchifyPrint ( String result ) {
         System . out . println ( result ) ;
     }
 
     // Method-2: Join Array using Java8 Stream operation
     private static void joinArrayUsingJava8Stream ( ) {
         String [ ] company1 = new String [ ] { "google" , "twitter" } ;
         String [ ] company2 = new String [ ] { "apple" , "microsoft" } ;
 
         // Stream.of() - returns a sequential ordered stream whose elements are the specified values.
         // A sequence of elements supporting sequential and parallel aggregate operations. The following example illustrates an aggregate operation using Stream and IntStream:
         //
         //     int sum = widgets.stream()
         //                      .filter(w -> w.getColor() == RED)
         //                      .mapToInt(w -> w.getWeight())
         //                      .sum();
         String [ ] result = Stream . of ( company1 , company2 ) . flatMap ( Stream : : of ) . toArray ( String [ ] : : new ) ;
         crunchifyPrint ( "\nFrom Method-2: Stream.of() ==> " + Arrays . toString ( result ) ) ;
 
         int [ ] crunchifyArray1 = new int [ ] { 111 , 444 } ;
         int [ ] crunchifyArray2 = new int [ ] { 222 , 555 } ;
 
         // Arrays.stream() - returns a sequential IntStream with the specified array as its source.
         int [ ] crunchifyResult2 = IntStream . concat ( Arrays . stream ( crunchifyArray1 ) , Arrays . stream ( crunchifyArray2 ) ) . toArray ( ) ;
 
         crunchifyPrint ( "From Method-2: IntStream.concat() ==> " + Arrays . toString ( crunchifyResult2 ) ) ;
     }
 
     // Method-3: Join Array using Standard Java APIs
     private static void joinArrayUsingJavaAPI ( ) {
         String [ ] company1 = new String [ ] { "google" , "twitter" } ;
         String [ ] company2 = new String [ ] { "apple" , "microsoft" } ;
 
         String [ ] crunchifyResult = crunchifyJoinGenericArray ( company1 , company2 ) ;
 
         crunchifyPrint ( "\nFrom Method-3: crunchifyJoinArrayusingGeneric() ==> " + Arrays . toString ( crunchifyResult ) ) ;
 
         int [ ] crunchifyArray1 = new int [ ] { 111 , 444 } ;
         int [ ] crunchifyArray2 = new int [ ] { 222 , 555 } ;
 
         int [ ] crunchifyResult2 = crunchifyJoinIntegerArray ( crunchifyArray1 , crunchifyArray2 ) ;
 
         // Arrays.toString() Returns a string representation of the contents of the specified array.
         // The string representation consists of a list of the array's elements, enclosed in square brackets ("[]").
         // Adjacent elements are separated by the characters ", " (a comma followed by a space).
         // Elements are converted to strings as by String.valueOf(int). Returns "null" if a is null.
         crunchifyPrint ( "From Method-3: joinArray() ==> " + Arrays . toString ( crunchifyResult2 ) ) ;
     }
 
     @ SafeVarargs
     private static < T > T [ ] crunchifyJoinGenericArray ( T [ ] . . . crunchifyArrays ) {
         int crunchify = 0 ;
         for ( T [ ] crunchifyArray : crunchifyArrays ) {
             crunchify += crunchifyArray . length ;
         }
 
         //T[] result = new T[crunchify];
         final T [ ] crunchifyResult = ( T [ ] ) Array . newInstance ( crunchifyArrays [ 0 ] . getClass ( ) . getComponentType ( ) ,
                 crunchify ) ;
 
         int crunchifyOffset = 0 ;
         for ( T [ ] crunchifyArray : crunchifyArrays ) {
 
             // Copies an array from the specified source array, beginning at the specified position, to the specified position of the destination array.
             // A subsequence of array components are copied from the source array referenced by src to the destination array referenced by dest.
             // The number of components copied is equal to the length argument.
             // The components at positions srcPos through srcPos+length-1 in the source array are copied into positions destPos through destPos+length-1, respectively, of the destination array.
             System . arraycopy ( crunchifyArray , 0 , crunchifyResult , crunchifyOffset , crunchifyArray . length ) ;
             crunchifyOffset += crunchifyArray . length ;
         }
 
         return crunchifyResult ;
     }
 
     private static int [ ] crunchifyJoinIntegerArray ( int [ ] . . . crunchifyArrays ) {
         int crunchify = 0 ;
         for ( int [ ] crunchifyArray : crunchifyArrays ) {
             crunchify += crunchifyArray . length ;
         }
 
         final int [ ] crunchifyResult = new int [ crunchify ] ;
 
         int crunchifyOffset = 0 ;
         for ( int [ ] crunchifyArray : crunchifyArrays ) {
 
             System . arraycopy ( crunchifyArray , 0 , crunchifyResult , crunchifyOffset , crunchifyArray . length ) ;
             crunchifyOffset += crunchifyArray . length ;
         }
 
         return crunchifyResult ;
     }
 
}

Jetons un coup d'œil à certains détails de l'API Java.

java.lang.System.arraycopy() :

Exemple de copie de tableau Java

java.util.Arrays.toString() :

Java toString Exemple

java.util.stream() :

Java Stream.of Exemple
Exemple de flux Java

Exécutez simplement le programme en tant que programme Java et vous devriez voir un résultat identique à celui ci-dessous.

Sortie de la console IntelliJ IDEA :

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
/ Library / Java / JavaVirtualMachines / jdk - 15.jdk / Contents / Home / bin / java - javaagent : / Applications / IntelliJ IDEA . app / Contents / lib / idea_rt . jar = 50249 : / Applications / IntelliJ IDEA . app / Contents / bin - Dfile . encoding = UTF - 8 - classpath / Users / app / crunchify / github / CrunchifyTutorials / target / classes : / Users / app / crunchify / github / CrunchifyTutorials / WebContent / WEB - INF / lib / zxing - 2.1.jar / Users / app / . m2 / repository / commons - collections / commons - collections / 3.2.1 / commons - collections - 3.2.1.jar / spring - context - support - 5.1.3.RELEASE.jar crunchify . com . tutorial . CrunchifyJoinArrays3Ways
 
Original String Array1 : [ google , twitter ]
Original String Array2 : [ apple , microsoft ]
Original Integer Array1 : [ 111 , 444 ]
Original Integer Array2 : [ 222 , 555 ]
 
From Method - 1 : addAll ( ) - String == > [ google , twitter , apple , microsoft ]
From Method - 1 : addAll ( ) - Integer == > [ 111 , 444 , 222 , 555 ]
 
From Method - 2 : Stream . of ( ) == > [ google , twitter , apple , microsoft ]
From Method - 2 : IntStream . concat ( ) == > [ 111 , 444 , 222 , 555 ]
 
From Method - 3 : crunchifyJoinArrayusingGeneric ( ) == > [ google , twitter , apple , microsoft ]
From Method - 3 : joinArray ( ) == > [ 111 , 444 , 222 , 555 ]
 
Process finished with exit code 0

Veuillez me faire savoir si vous avez un autre moyen de fusionner des tableaux Java ou si vous obtenez une exception.