Beautiful

example.java

private static final Splitter newlineSplitter = Splitter.on(Pattern.compile("\r?\n"));
private static final Splitter spaceSplitter = Splitter.on(CharMatcher.whitespace()).omitEmptyStrings();

Map<String, String> substitutions = newlineSplitter
  .splitToList(text)
  .stream()
  .map(spaceSplitter::splitToList)
  .filter(r -> r.size() != 0)
  .collect(Collectors.toMap(
          ss -> ss.get(0),
          ss -> ss.get(1)
  ));

example.kt

val substitutions = text.split(Pattern.compile("\r?\n"))
  .map { it.split(' ') }
  .filter { it.isNotEmpty() }
  .associate { it[0] to it[1] }

Takes input

123 456
789 101112

and converts to a map

{
123: 456,
789: 101112
}