Java读取txt文件到hashmap，用“：”分割
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Java read txt file to hashmap, split by ":"
提问by Casper TL
I have a txt file with the form:
我有一个格式为 txt 的文件：
Key:value
Key:value
Key:value
...
I want to put all the keys with their value in a hashMap that I've created. How do I get a FileReader(file)or Scanner(file)to know when to split up the keys and values at the colon (:) ? :-)
我想将所有键及其值放在我创建的 hashMap 中。我如何获得FileReader(file)或Scanner(file)知道何时在冒号 (:) 处拆分键和值？:-)
I've tried:
我试过了：
Scanner scanner = new scanner(file).useDelimiter(":");
HashMap<String, String> map = new Hashmap<>();
while(scanner.hasNext()){
map.put(scanner.next(), scanner.next());
}
采纳答案by trooper
Read your file line-by-line using a BufferedReader, and for each line perform a spliton the first occurrence of :within the line (and if there is no :then we ignore that line).
使用 a 逐行读取您的文件BufferedReader，并对每一行在该行内split第一次出现时执行 a :（如果没有，:则我们忽略该行）。
Here is some example code - it avoids the use of Scanner (which has some subtle behaviors and imho is actually more trouble than its worth).
这是一些示例代码 - 它避免使用 Scanner （它有一些微妙的行为，恕我直言实际上比它的价值更麻烦）。
public static void main( String[] args ) throws IOException
{
String filePath = "test.txt";
HashMap<String, String> map = new HashMap<String, String>();
String line;
BufferedReader reader = new BufferedReader(new FileReader(filePath));
while ((line = reader.readLine()) != null)
{
String[] parts = line.split(":", 2);
if (parts.length >= 2)
{
String key = parts[0];
String value = parts[1];
map.put(key, value);
} else {
System.out.println("ignoring line: " + line);
}
}
for (String key : map.keySet())
{
System.out.println(key + ":" + map.get(key));
}
reader.close();
}
回答by beresfordt
The below will work in java 8.
下面将在 java 8 中工作。
The .filter(s -> s.matches("^\\w+:\\w+$"))will mean it only attempts to work on line in the file which are two strings separated by :, obviously fidling with this regex will change what it will allow through.
这.filter(s -> s.matches("^\\w+:\\w+$"))意味着它只尝试在文件中在线工作，这两个字符串由 分隔:，显然摆弄这个正则表达式会改变它允许通过的内容。
The .collect(Collectors.toMap(k -> k.split(":")[0], v -> v.split(":")[1]))will work on any lines which match the previous filter, split them on :then use the first part of that split as the key in a map entry, then the second part of that split as the value in the map entry.
在.collect(Collectors.toMap(k -> k.split(":")[0], v -> v.split(":")[1]))将上匹配以前的过滤器的任何行工作，将它们分割上:然后使用该分割如在图条目中的密钥，则该分割如在图条目中的值的第二部分的第一部分。
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Map;
import java.util.stream.Collectors;
public class Foo {
public static void main(String[] args) throws IOException {
String filePath = "src/main/resources/somefile.txt";
Path path = FileSystems.getDefault().getPath(filePath);
Map<String, String> mapFromFile = Files.lines(path)
.filter(s -> s.matches("^\w+:\w+"))
.collect(Collectors.toMap(k -> k.split(":")[0], v -> v.split(":")[1]));
}
}
回答by Oleg Mikhailov
One more JDK 1.8 implementation.
又一个 JDK 1.8 实现。
I suggest using try-with-resources and forEachiterator with putIfAbsent()method to avoid java.lang.IllegalStateException: Duplicate key valueif there are some duplicate values in the file.
我建议使用 try-with-resources 和forEachiterator with putIfAbsent()method 来避免java.lang.IllegalStateException: Duplicate key value如果文件中有一些重复值。
FileToHashMap.java
FileToHashMap.java
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Map;
import java.util.HashMap;
import java.util.stream.Stream;
public class FileToHashMap {
public static void main(String[] args) throws IOException {
String delimiter = ":";
Map<String, String> map = new HashMap<>();
try(Stream<String> lines = Files.lines(Paths.get("in.txt"))){
lines.filter(line -> line.contains(delimiter)).forEach(
line -> map.putIfAbsent(line.split(delimiter)[0], line.split(delimiter)[1])
);
}
System.out.println(map);
}
}
in.txt
.txt
Key1:value 1
Key1:duplicate key
Key2:value 2
Key3:value 3
The output is:
输出是：
{Key1=value 1, Key2=value 2, Key3=value 3}
