如何迭代multimap以使用java在CSV文件中以插入順序編寫鍵和值？

Question

Set keySet = myMultimap.keySet(); 
Iterator keyIterator = keySet.iterator(); 
while (keyIterator.hasNext()) { 
    String key = (String) keyIterator.next(); 
    List values = (List) myMultimap.get(key); 
    System.out.println("keyname " + key); 
    System.out.println("values " + values); 
} 

上述迭代產生的結果以下列順序

keyname id 
values [1517049512, 102888752, 102888762, 1558590692, 1516493341, 1555855832, 1557068421, 1557460861, 1570321872, 1582701092] 
keyname suspended 
values [false, false, false, false, false, false, false, false] 

預期的結果應該是在形式

id   suspended  
1517049512 false 
..... 
1582701092 false 

並將其導出到CSV，我用下面的代碼。

Set<String> keys = myMultimap.keySet();   
FileWriter writer = new FileWriter("D:/Csvfile/users.csv"); 
for (String keyname : keys) { 
    writer.append(keyname); 
    writer.append(","); 
} 
writer.append("\n")   
for (String keyname : keys) { 
    String result = myMultimap.values().toString(); 
    writer.append(result); 
    writer.append("\n"); 
} 

我正在使用番石榴multimap。

任何人都可以幫助我將multimap鍵和值以正確的順序導出到CSV文件嗎？

如果我使用上面的代碼，在我的CSV文件中，我的密鑰標頭不是重複的，但我的值是重複的。鍵值對應在CSV文件中按上述順序排列。

Answer 1

唯一的問題是地圖沒有排序。當一套鑰匙 - 這是一套，無序的。因此你必須定義一些命令。

該解決方案按照您的預期打印數據。您只需將System.out.print替換爲輸出到文件（或將其全部收集到一個字符串中並在最後執行一次寫入）。

import com.google.common.collect.ArrayListMultimap; 
import com.google.common.collect.Multimap; 

import java.util.Arrays; 
import java.util.List; 

import static java.util.Arrays.stream; 
import static java.util.Comparator.comparingInt; 
import static java.util.stream.Collectors.joining; 

public class Main { 

    public static void main(String[] args) { 
     Multimap<String, Object> myMultimap = newMultiMap(); 

     String[] keys = myMultimap.keySet().stream().sorted().toArray(String[]::new); 
     List<?>[] values = stream(keys).map(myMultimap::get).toArray(List[]::new); 
     int maxLength = stream(values).map(List::size).max(comparingInt(i -> i)).get(); 

     System.out.println(stream(keys).collect(joining("\t"))); 
     for (int line = 0; line < maxLength; line++) { 
      for (List<?> value : values) { 
       if (line < value.size()) { 
        System.out.print(value.get(line)); 
       } else { 
        System.out.print("\t"); 
       } 
       System.out.print("\t"); 
      } 
      System.out.println(); 
     } 
    } 

    private static Multimap<String, Object> newMultiMap() { 
     Multimap<String, Object> myMultimap = ArrayListMultimap.create(); 

     myMultimap.put("id", 1517049512); 
     myMultimap.put("id", 102888752); 
     myMultimap.put("id", 102888762); 
     myMultimap.put("id", 1558590692); 
     myMultimap.put("id", 1516493341); 
     myMultimap.put("id", 1555855832); 
     myMultimap.put("id", 1557068421); 
     myMultimap.put("id", 1557460861); 
     myMultimap.put("id", 1570321872); 
     myMultimap.put("id", 1582701092); 

     myMultimap.put("suspended", false); 
     myMultimap.put("suspended", false); 
     myMultimap.put("suspended", false); 
     myMultimap.put("suspended", false); 
     myMultimap.put("suspended", false); 
     myMultimap.put("suspended", false); 
     myMultimap.put("suspended", false); 
     myMultimap.put("suspended", false); 

     myMultimap.put("verified", true); 
     myMultimap.put("verified", true); 
     myMultimap.put("verified", true); 
     myMultimap.put("verified", true); 
     myMultimap.put("verified", true); 
     myMultimap.put("verified", true); 
     myMultimap.put("verified", true); 
     myMultimap.put("verified", true); 

     return myMultimap; 
    } 

} 

輸出：

id suspended verified 
1517049512 false true 
102888752 false true 
102888762 false true 
1558590692 false true 
1516493341 false true 
1555855832 false true 
1557068421 false true 
1557460861 false true 
1570321872 
1582701092     

編輯：

寫入文件，只需用一個其寫入文件替換印刷循環。您可能需要更改行分隔符。

try (FileWriter writer = new FileWriter("D:/Csvfile/users.csv");) { 
    writer.append(stream(keys).collect(joining(","))); 
    writer.append("\r\n"); 
    for (int line = 0; line < maxLength; line++) { 
     for (int i = 0; i < values.length; i++) { 
      List<?> value = values[i]; 
      if (i != 0) { 
       writer.append(","); 
      } 
      if (line < value.size()) { 
       writer.append(String.valueOf(value.get(line))); 
      } 
     } 
     writer.append("\r\n"); 
    } 
} catch (IOException e) { 
    throw new RuntimeException(e); 
} 

Answer 2

Set keySet = myMultimap.keySet(); 
Iterator keyIterator = keySet.iterator(); 

int maxLenght=-1; 

// loop to get max number of rows 
// and print Keys 
while (keyIterator.hasNext()) { 
    String key = (String) keyIterator.next(); 
    List values = (List) myMultimap.get(key); 
    maxLenght = Math.Max(maxLenght , values.size()); 
    System.out.print(Key + "\t"); 
} 

System.out.println();  // new line 
keyIterator = keySet.iterator();// reset Iterator 

// loop and print data row by row 
for(int i=0 ; i<maxLenght ; i++){ 
    while (keyIterator.hasNext()){ 
     String key = (String) keyIterator.next(); 
     List values = (List) myMultimap.get(key); 
     if(values.size() < i){ 
      System.out.print(values.get(i) + "\t"); 
     } 
     else{ 
      System.out.print("\t\t"); 
     } 
    } 
} 

在你的榜樣