În Java, cum să vă alăturați Arrays? 3 moduri: Apache Commons ArrayUtils, Java 8 Streams și API-uri simple

Publicat: 2022-01-20
În Java, cum să vă alăturați Arrays? 3 moduri - Apache Commons ArrayUtils, Java 8 Streams și API-uri simple

În acest tutorial vom analiza diferite moduri prin care ne putem alătura matricelor Java.

Dacă aveți oricare dintre întrebările de mai jos, vă aflați la locul potrivit:

  • Cum pot concatena două matrice în Java?
  • Cum se îmbină două matrice în Java?
  • 3 moduri de a combina matrice în Java
  • Alăturați-vă Array of Primitives cu Separator în Java

Iată cele trei moduri în care ați putea să vă alăturați matricelor în Java.

  1. Alăturați-vă Array folosind utilitarul Apache Common
  2. Alăturați-vă Array folosind operația Java8 Stream
  3. Alăturați-vă Array folosind API-urile Java standard

Să începem:

Creați clasa java CrunchifyJoinArrays3Ways.java .

Puneți sub codul Java în fișier.

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 ;
     }
 
}

Să aruncăm o privire la câteva dintre detaliile API-ului Java.

java.lang.System.arraycopy():

Exemplu Java arrayCopy

java.util.Arrays.toString():

Exemplu Java toString

java.util.stream():

Java Stream.de exemplu
Exemplu de flux Java

Doar rulați programul ca program Java și ar trebui să vedeți un rezultat la fel ca mai jos.

Ieșirea consolei 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

Vă rog să-mi spuneți dacă aveți vreo altă modalitate de a îmbina Java Arrays sau obțineți vreo excepție.