Java read txt file to hashmap, split by “:”

Question

I have a txt file with the form:

Key:value
Key:value
Key:value
...

I want to put all the keys with their value in a hashMap that I\'ve crea

Answer 1

One more JDK 1.8 implementation.

I suggest using try-with-resources and forEach iterator with putIfAbsent() method to avoid java.lang.IllegalStateException: Duplicate key value if there are some duplicate values in the file.

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 map = new HashMap<>();

        try(Stream 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

Key1:value 1
Key1:duplicate key
Key2:value 2
Key3:value 3

The output is:

{Key1=value 1, Key2=value 2, Key3=value 3}