import java.util.Map;
import java.util.List;
import java.util.Arrays;
import java.util.Collection;
import java.util.stream.Stream;
import java.util.stream.Collectors;
public class MyClass {
public static void main(String args[]) {
String[] arr = new String[] { "java", "c", "c#", "c++", "rust", "python", "php"};
Map<Integer, List<String>> mp = Arrays.stream(arr)
.collect(Collectors.groupingBy(String::length));
for (Map.Entry<Integer, List<String>> e : mp.entrySet()) {
System.out.println(e);
}
}
}
/*
run:
1=[c]
2=[c#]
3=[c++, php]
4=[java, rust]
6=[python]
*/