Wie kann man in Java Arrays beitreten? 3 Möglichkeiten: Apache Commons ArrayUtils, Java 8 Streams und einfache APIs

Veröffentlicht: 2022-01-20

In diesem Tutorial werden wir verschiedene Möglichkeiten erläutern, wie wir Java-Arrays beitreten können.

Wenn Sie eine der folgenden Fragen haben, dann sind Sie hier richtig:

Wie kann ich zwei Arrays in Java verketten?
Wie füge ich zwei Arrays in Java zusammen?
3 Möglichkeiten zum Kombinieren von Arrays in Java
Join Array of Primitives with Separator in Java

Hier sind die drei Möglichkeiten, wie Sie Arrays in Java verbinden können.

Verbinden Sie das Array mit dem Apache Common-Dienstprogramm
Join-Array mit Java8-Stream-Operation
Join-Array mit Standard-Java-APIs

Lass uns anfangen:

Erstellen Sie die Java-Klasse CrunchifyJoinArrays3Ways.java .

Fügen Sie den folgenden Java-Code in die Datei ein.

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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 ;

}

Werfen wir einen Blick auf einige Java-API-Details.

java.lang.System.arraycopy():

java.util.Arrays.toString():

java.util.stream():

Führen Sie das Programm einfach als Java-Programm aus und Sie sollten das gleiche Ergebnis wie unten sehen.

Ausgabe der IntelliJ IDEA-Konsole:

/ 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

Bitte lassen Sie mich wissen, wenn Sie eine andere Möglichkeit haben, Java-Arrays zusammenzuführen, oder wenn Sie eine Ausnahme erhalten.