java 如何将 List<Object> 转换为逗号分隔的字符串
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How to convert List<Object> into comma separated String
提问by user9193174
I am getting list of Addressobjects from the DB call.
我正在Address从数据库调用中获取对象列表。
ArrayList<Address> addresses = new ArrayList<>();
Each Addresshas an int addressIdproperty.
每个人Address都有一个int addressId属性。
I am writing an update query where in the INclause I am sending this whole list of Addressobjects and I am getting ibatis TypeException. How can I convert List<Address>to a comma separated string which can be sent to update query?
我正在写一个更新查询，在IN我发送整个Address对象列表的子句中，我得到了 ibatis TypeException。如何转换List<Address>为可以发送到更新查询的逗号分隔字符串？
My update query looks like:::
我的更新查询看起来像:::
Update tablename set postcode = #{postCode} where id in #{addressID}.
回答by Kirill Simonov
Using Java 8 you could do it in one line:
使用 Java 8，您可以在一行中完成：
String addressID = addresses
.stream()
.map(a -> String.valueOf(a.addressId))
.collect(Collectors.joining(","));
回答by mohsenJsh
for converting to comma seperated String use something like this:
要转换为逗号分隔的字符串，请使用以下内容：
String commaSeparatedStr = addresses
.stream()
.map(c -> String.valueOf(c))
.collect(Collectors.joining(","));
回答by Ravi
String#join, which accepts delimiter Stringand Iterableelements (which is Listin your case)
String#join，它接受分隔符String和Iterable元素（List在你的情况下）
List<String> strings = new LinkedList<>();
strings.add("Java");
strings.add("is");
strings.add("cool");
String message = String.join(",", strings); //pass delimiter and List
//message returned is: "Java,is,cool"
回答by Marit
Iterate over the address objects, retrieve their ID and create a String. Something like this:
遍历地址对象，检索它们的 ID 并创建一个字符串。像这样的东西：
StringBuilder sb = new StringBuilder();
for (Address a: adresses) {
sb.append(a.getId());
sb.append(", ");
}
String ids = sb.toString();
回答by Nithin
The format required can be obtained using toString()and replaceAll()methods (using regular Expressions).
可以使用toString()和replaceAll()方法（使用正则表达式）获得所需的格式。
String addressString = addresses.toString().replaceAll("[ \[ \] ]", "");
回答by xavierz
List of int- let Java do it:
列表int- 让 Java 来做：
String tmp = addresses.toString();
String csList = tmp.substring(1, tmp.length()-1);
回答by Usman
String.join(", ", addresses) ;
回答by Zico
StringBuilder addressIds = new StringBuilder("");
for(Address address : addresses){
if (addressIds.length() > 1)
addressIds.append(", ");
addressIds.append("'").append(address.id()).append("'");
}
//in this method you can directly send the string in Update tablename + set postcode + where id in <String>.
methodOfUpdateInQuery(addressIds.toString());
