将 java Map 转换为自定义 key=value 字符串
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Convert java Map to custom key=value string
提问by karolkpl
I have TreeMap<String,String>which I need to convert to URI-like string and then back to Map.
I need to set custom delimiters.
我TreeMap<String,String>需要将其转换为类似 URI 的字符串，然后再转换回 Map。我需要设置自定义分隔符。
Is there any tool (Guava, Apache commons?) that can do it for me? I know, I can write simple loops, but I'm looking for one-liner :)
有什么工具（Guava，Apache commons？）可以为我做这件事吗？我知道，我可以编写简单的循环，但我正在寻找单行 :)
For example
例如
key value
key1 val1
key2 val2
key1_val1|key2_val2
采纳答案by zapl
According to David Tuligyou could do it in guava via
根据David Tulig 的说法，您可以通过在番石榴中做到这一点
String string = Joiner.on("|").withKeyValueSeparator("_").join(map);
The opposite is also available via
相反的也可以通过
Map<String, String> map = Splitter.on("|").withKeyValueSeparator("_").split(string);
回答by yurib
its not guava or apache commons, and it is a loop, but aside from instantiating the string builder, it is a one liner:
它不是番石榴或 apache 公共资源，它是一个循环，但除了实例化字符串生成器之外，它还是一个单行：
for (Entry<String,String> entry : myMap.entrySet()) {
sb.append(entry.getKey() + separator + entry.getValue() + "\n");
}
回答by jokster
Using Java8:
使用Java8：
private static Map<String, String> prepareMap() {
Map<String, String> map = new LinkedHashMap<>();
map.put("key1", "val1");
map.put("key2", "val2");
return map;
}
@Test
public void toStr() {
assertEquals("key1_val1|key2_val2", prepareMap().entrySet().stream()
.map(e -> e.getKey() + "_" + e.getValue())
.collect(Collectors.joining("|")));
}
@Test
public void toStrFunction() {
assertEquals("key1_val1|key2_val2", joiner("|", "_").apply(prepareMap()));
}
private static Function<Map<String, String>, String> joiner(String entrySeparator, String valueSeparator) {
return m -> m.entrySet().stream()
.map(e -> e.getKey() + valueSeparator + e.getValue())
.collect(Collectors.joining(entrySeparator));
}
@Test
public void toMap() {
assertEquals("{key1=val1, key2=val2}", Stream.of("key1_val1|key2_val2".split("\|"))
.map(e -> e.split("_", 2))
.collect(Collectors.toMap(e -> e[0], e -> e.length > 1 ? e[1] : null)).toString());
}
@Test
public void toMapFunction() {
assertEquals("{key1=val1, key2=val2}", splitter("\|", "_").apply("key1_val1|key2_val2").toString());
}
private static Function<String, Map<String, String>> splitter(String entrySeparator, String valueSeparator) {
return s -> Stream.of(s.split(entrySeparator))
.map(e -> e.split(valueSeparator, 2))
.collect(Collectors.toMap(e -> e[0], e -> e.length > 1 ? e[1] : null));
}
回答by Timo B?wing
In java 8 and up there is another way without external dependencies: use StringJoiner:
在 java 8 及更高版本中，还有另一种没有外部依赖的方法：使用StringJoiner：
List<String> cities = Arrays.asList("Milan",
"London",
"New York",
"San Francisco");
String citiesCommaSeparated = String.join(",", cities);
System.out.println(citiesCommaSeparated);
//Output: Milan,London,New York,San Francisco
Credits and example go to this URL (https://reversecoding.net/java-8-convert-list-string-comma/)
积分和示例转到此 URL (https://reversecoding.net/java-8-convert-list-string-comma/)
