import java.util.*;
import java.io.*;
 
class Ideone
{
    public static void main(String[] args) {
        final NavigableSet<String> set = new TreeSet<>(Arrays.asList("1.0", "1.1", "1.2", "3.0", "3.1", "4.0"));
        System.out.println("After 1.0: " + set.higher("1.0"));
        System.out.println("Before 1.0: " + set.lower("1.0"));
        System.out.println("After 1.1: " + set.higher("1.1"));
        System.out.println("Before 1.1: " + set.lower("1.1"));
        System.out.println("After 1.2: " + set.higher("1.2"));
        System.out.println("Before 1.2: " + set.lower("1.2"));
        System.out.println("After 4.0: " + set.higher("4.0"));
        System.out.println("Before 4.0: " + set.lower("4.0"));
    }
}

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