Java 8：如何将 String 转换为 Map<String,String>？
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Java 8: How to convert String to Map<String,String>?
提问by Phuong
I have a Map:
我有一张地图：
Map<String, String> utilMap = new HashMap();
utilMap.put("1","1");
utilMap.put("2","2");
utilMap.put("3","3");
utilMap.put("4","4");
I converted it to a String:
我将其转换为字符串：
String utilMapString = utilMap
.entrySet()
.stream()
.map(e -> e.toString()).collect(Collectors.joining(","));
Out put: 1=1,2=2,3=3,4=4,5=5
How to convert utilMapString to Map in Java8? Who can help me with?
如何在 Java8 中将 utilMapString 转换为 Map？谁能帮帮我？
采纳答案by user7
Split the string by ,to get individual map entries. Then split them by =to get the key and the value.
拆分字符串,以获取单个地图条目。然后将它们拆分=以获取键和值。
Map<String, String> reconstructedUtilMap = Arrays.stream(utilMapString.split(","))
.map(s -> s.split("="))
.collect(Collectors.toMap(s -> s[0], s -> s[1]));
Note:As pointed out by Andreas@ in the comments, this is not a reliable way to convert between a map and a string
注意：正如Andreas@ 在评论中指出的那样，这不是在地图和字符串之间进行转换的可靠方法
EDIT: Thanks to Holger for this suggestion.
编辑：感谢 Holger 的这个建议。
Use s.split("=", 2)to ensure that the array is never larger than two elements. This will be useful to not lose the contents (when the value has =)
使用s.split("=", 2)以确保阵列从来没有超过两个元素大。这对于不丢失内容很有用（当值有时=）
Example:when the input string is "a=1,b=2,c=3=44=5555"you will get {a=1, b=2, c=3=44=5555}
示例：当输入字符串为时，"a=1,b=2,c=3=44=5555"您将得到{a=1, b=2, c=3=44=5555}
Earlier (just using s.split("=")) will give
{a=1, b=2, c=3}
早些时候（只是使用s.split("=")）会给
{a=1, b=2, c=3}
回答by Amit
If you want to generate a map from String you can it with below way:
如果您想从 String 生成地图，您可以使用以下方式：
Map<String, String> newMap = Stream.of(utilMapString.split("\,"))
.collect(Collectors.toMap(t -> t.toString().split("=")[0], t -> t.toString().split("=")[1]));
回答by Tim Biegeleisen
Here is another option which streams a list of 1=1etc. terms into a map.
这是另一个选项，它将等项列表流式传输1=1到地图中。
String input = "1=1,2=2,3=3,4=4,5=5";
Map<String, String> map = Arrays.asList(input.split(",")).stream().collect(
Collectors.toMap(x -> x.replaceAll("=\d+$", ""),
x -> x.replaceAll("^\d+=", "")));
System.out.println(Collections.singletonList(map));
[{1=1, 2=2, 3=3, 4=4, 5=5}]
回答by Azee
If the sequence may contain values with the same key - use
如果序列可能包含具有相同键的值 - 使用
Map<String, String> skipDuplicatesMap = Stream.of("1=1,2=2,3=3,4=4,5=5".split(",")).
map(el -> el.split("=")).
collect(toMap(arr -> arr[0], arr -> arr[1], (oldValue, newValue) -> oldValue));
