Java代码如何连接两个数组呢?

下文笔者讲述使用java代码组合两个数组的方法及示例分享,如下所示

连接数组的实现思路

数组组合的实现思路:
    方式1:
	  使用Apache Commons Lang库中的ArrayUtils.addAll
	    组合两个数组,此方法支持基本数据类型和对象数据类型
	方式2:
	  使用原生的Java API组合数组
    方式3:
	   使用Stream.of组合数组

例:数组组合的示例分享

Apache Commons Lang之ArrayUtils

package com.java265.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));
    }
}

注意事项: 
    maven项目可使用以下方式引入jar包
    <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-lang3</artifactId>
      <version>3.4</version>
   </dependency>

Java API的方式组合数组

纯Java API示例同时支持原始类型和泛型类型。

package com.java265.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> 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) 
}

Java 8 Stream的方式连接数组

package com.java265.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));
    }
}