java怎么将2个数组的数据合并？
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concat怎么用？
int a[]=1,7,9,11,13,15,17,19;
int b[]=2,4,6,8,10;
concat（）用法：
String a="abc";
String b="edf";
String c=a.concat(b);
c的值为“abcdef"
数组可以用for循环合并:
public static void main(String[] args)
int a[]=1,7,9,11,13,15,17,19;
int b[]=2,4,6,8,10;
int aL=a.length;
int bL=b.length;
int lenght=aL+bL;
int[] c=new int[lenght];
for(int i=0;i<lenght;i++)
if(i<aL)//
c[i]=a[i];
else
c[i]=b[i-aL];
for(int i=0;i<c.length;i++)
System.out.print(c[i]+" ");
参考技术A
不记得有可以合并两个数组的方法，感觉基本只能手动了，如：
int index=0;int c[]=new int[a.length+b.length];
for(int i=0;i<a.length;i++)
c[index++]=a[i];
for(int i=0;i<b.length;i++)
c[index++]=b[i];
追问
运行错误
追答public class Testpublic static void main(String[] args)
int a[]=1,7,9,11,13,15,17,19;
int b[]=2,4,6,8,10;
int index=0;
int c[]=new int[a.length+b.length];
for(int i=0;i<a.length;i++)
c[index++]=a[i];
for(int i=0;i<b.length;i++)
c[index++]=b[i];
//打印合并后的数组C
for(int i=0;i<c.length;i++)
System.out.print("c["+i+"]="+c[i]+" ");
本回答被提问者和网友采纳 参考技术B int a[]=1,7,9,11,13,15,17,19;
int b[]=2,4,6,8,10;
ArrayList<Integer> alist=new ArrayList<Integer>(a.length+b.length);
for (int j = 0; j < a.length; j++)
alist.add(a[j]);
for (int k = 0; k < b.length; k++)
alist.add(b[k]);
int c[] =new int[alist.size()];
for(int i=0; i<alist.size();i++)
c[i]=alist.get(i);
参考技术C concat是String类型的，无法在integer型数组上使用
基于共同元素合并 2 个数组
【中文标题】基于共同元素合并 2 个数组【英文标题】：Merge 2 arrays based on a common element 【发布时间】：2021-12-05 21:18:12 【问题描述】：所以我有一个拉入 2 个数组的 Laravel 控制器。
数组 1：
[
"id":1,
"created_at":null,
"updated_at":null,
"name":"The Darkroom",
"description":"This is the room your parents warned you about",
"image":"https:\/\/images.unsplash.com\/photo-1579662908513-50e1433a258a?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=1234&q=80",
"is_private":"0"
,
"id":2,
"created_at":null,
"updated_at":null,
"name":"Smoking & Cigars",
"description":"Time to light up and enjoy a cigar!",
"image":"https:\/\/images.unsplash.com\/photo-1617850136763-06bc0a9a089c?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=2000&q=80",
"is_private":"0"
,
"id":3,
"created_at":null,
"updated_at":null,
"name":"Humiliation",
"description":"today is the day you are going to be exposed",
"image":"https:\/\/images.unsplash.com\/photo-1571570261702-3d23956fa32e?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=2600&q=80",
"is_private":"1"
,
"id":4,
"created_at":null,
"updated_at":null,
"name":"Financial Domination",
"description":"hand over your cash and say thank you Sir!",
"image":"https:\/\/images.unsplash.com\/photo-1526304640581-d334cdbbf45e?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=2200&q=80",
"is_private":"0"
,"id":5,"created_at":null,"updated_at":null,"name":"Pups & Handlers","description":"Woof, woof, bark, sit","image":"https:\/\/images.unsplash.com\/photo-1506939754500-f27bc71fccd4?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=2200&q=80","is_private":"1"]
数组 2：
"channels":"presence-chat.1":"user_count":1,"presence-chat.4":"user_count":1
最终数组应如下所示：
[
"id":1
"other data in the first array"
"user_count": 1
]
我需要在控制器中做的是将数据合并到一个数组中。因此，理想情况下，取第二个数组，将 chat.ID 与第一个数组的 ID 匹配，然后将 user_count 添加到其中......好吧，你明白我的意思了。
我以前从未这样做过，所以我不知道如何最好地解决这个问题。任何帮助将永远感激！
【问题讨论】：
你能告诉我们你希望最终的数组如何作为一个例子吗？ 【参考方案1】：给你，这里假设presence-chat.4 表示id 为4 的频道：
<?php
$json1 = '["id":1,"created_at":null,"updated_at":null,"name":"The Darkroom","description":"This is the room your parents warned you about","image":"https:\/\/images.unsplash.com\/photo-1579662908513-50e1433a258a?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=1234&q=80","is_private":"0","id":2,"created_at":null,"updated_at":null,"name":"Smoking & Cigars","description":"Time to light up and enjoy a cigar!","image":"https:\/\/images.unsplash.com\/photo-1617850136763-06bc0a9a089c?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=2000&q=80","is_private":"0","id":3,"created_at":null,"updated_at":null,"name":"Humiliation","description":"today is the day you are going to be exposed","image":"https:\/\/images.unsplash.com\/photo-1571570261702-3d23956fa32e?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=2600&q=80","is_private":"1","id":4,"created_at":null,"updated_at":null,"name":"Financial Domination","description":"hand over your cash and say thank you Sir!","image":"https:\/\/images.unsplash.com\/photo-1526304640581-d334cdbbf45e?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=2200&q=80","is_private":"0","id":5,"created_at":null,"updated_at":null,"name":"Pups & Handlers","description":"Woof, woof, bark, sit","image":"https:\/\/images.unsplash.com\/photo-1506939754500-f27bc71fccd4?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=2200&q=80","is_private":"1"]';
$json2 = '"channels":"presence-chat.1":"user_count":1,"presence-chat.4":"user_count":1';
// convert the json into php arrays
$array1 = json_decode($json1, true);
$array2 = json_decode($json2, true);
// we extract the user_counts from the second array
// and make the index of a new array the channel id with value user_count
$channel_counts = [];
foreach ($array2['channels'] as $chan_name => $count)
$channel_id = explode('.', $chan_name)[1];
$user_count = $count['user_count'];
$channel_counts[$channel_id] = $user_count;
// we pass this array by reference as we are modifying it
foreach ($array1 as &$channel)
$id = $channel['id'];
if (isset($channel_counts[$id]))
$channel['user_count'] = $channel_counts[$id];
else
$channel['user_count'] = 0;
unset($channel);
$final_json = json_encode($array1, JSON_PRETTY_PRINT);
echo $final_json;
结果：
[
"id": 1,
"created_at": null,
"updated_at": null,
"name": "The Darkroom",
"description": "This is the room your parents warned you about",
"image": "https:\/\/images.unsplash.com\/photo-1579662908513-50e1433a258a?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=1234&q=80",
"is_private": "0",
"user_count": 1
,
"id": 2,
"created_at": null,
"updated_at": null,
"name": "Smoking & Cigars",
"description": "Time to light up and enjoy a cigar!",
"image": "https:\/\/images.unsplash.com\/photo-1617850136763-06bc0a9a089c?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=2000&q=80",
"is_private": "0",
"user_count": 0
,
"id": 3,
"created_at": null,
"updated_at": null,
"name": "Humiliation",
"description": "today is the day you are going to be exposed",
"image": "https:\/\/images.unsplash.com\/photo-1571570261702-3d23956fa32e?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=2600&q=80",
"is_private": "1",
"user_count": 0
,
"id": 4,
"created_at": null,
"updated_at": null,
"name": "Financial Domination",
"description": "hand over your cash and say thank you Sir!",
"image": "https:\/\/images.unsplash.com\/photo-1526304640581-d334cdbbf45e?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=2200&q=80",
"is_private": "0",
"user_count": 1
, ...snip
]
【讨论】：
所以这和你给出的代码一样工作得很好，但是当我用我用来抓取数组的代码替换 json2 时，它给了我错误 "json_decode(): Argument #1 ($json ) 必须是字符串类型，stdClass given" 但是如果我返回数组，它就会显示，就像我将它粘贴到我的问题中一样。所以是的，你有正确的答案我只是不知道为什么它不适合我 你是如何获得 JSON 数组的？ 在数组失败的情况下......它正在使用推送器 HTTP API - $pusherUserCount = $pusher->getChannels(['filter_by_prefix' => 'presence-', 'info' => 'user_count']) - 正如我所说 - 如果我返回 $pusherUserCount 它会显示数组，就像你在上面使用它一样 好的，试试$array2 = $pusher->getChannels(<snip>)->channels，去掉json_decode
不，仍然没有这样做。我要乱搞，看看是什么原因造成的。就像我说的那样，我已经尝试过使用您发布的静态数组并且它有效，我已经获取了数组并将其在线转换为 PHP 数组并且有效。所以我不确定这里有什么区别。以上是关于java怎么将2个数组的数据合并？的主要内容，如果未能解决你的问题，请参考以下文章
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