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In Java come unire gli array? 3 modi: Apache Commons ArrayUtils, Java 8 Streams e API semplici

Pubblicato: 2022-01-20
In Java come unire gli array? 3 modi: Apache Commons ArrayUtils, Java 8 Streams e API semplici

In questo tutorial esamineremo diversi modi in cui possiamo unire Java Arrays.

Se hai una delle seguenti domande, sei nel posto giusto:

  • Come posso concatenare due array in Java?
  • Come unire due array in Java?
  • 3 modi per combinare array in Java
  • Unisciti a Array of Primitives con Separator in Java

Ecco i tre modi in cui potresti unire gli array in Java.

  1. Unisciti all'array utilizzando l'utilità Apache Common
  2. Unisciti all'array utilizzando l'operazione Java8 Stream
  3. Unisciti all'array utilizzando le API Java standard

Iniziamo:

Crea classe java CrunchifyJoinArrays3Ways.java .

Inserisci sotto il codice Java nel file.

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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 ;
     }
 
}

Diamo un'occhiata ad alcuni dettagli dell'API Java.

java.lang.System.arraycopy():

Esempio di copia array Java

java.util.Arrays.toString():

Esempio Java toString

java.util.stream():

Esempio Java Stream.of
Esempio di flusso Java

Basta eseguire il programma come un programma Java e dovresti vedere un risultato come di seguito.

Uscita console IntelliJ IDEA:

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/ 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

Per favore fatemi sapere se avete qualche altro modo per unire array Java o ottenete qualche eccezione.