import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Main {
Matcher m = Pattern.compile("(?:^|(?<=\\s))(?=(\\S+\\s+\\S+)(?=\\s|$))")
.matcher("word1 word2 word3 word4");
while (m.find()) {
System.
out.
println(m.
group(1)); }
}
}
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