The challenge

Given a variable n,

If n is an integer, Return a string with dash'-'marks before and after each odd integer, but do not begin or end the string with a dash mark. If n is negative, then the negative sign should be removed.

If n is not an integer, return an empty value.

Ex:

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dashatize(274) -> '2-7-4'
dashatize(6815) -> '68-1-5'

The solution in Java code

Option 1:

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public class Solution {
    public static String dashatize(int num) {
      String n = String.valueOf(Math.abs(num)).replaceAll("-", "");
      return java.util.Arrays.asList(n.split("")).stream()
        .map(ch -> Integer.valueOf(ch) % 2 !=0 ? "-"+ch+"-" : ch)
        .collect(java.util.stream.Collectors.joining(""))
        .replaceAll("--", "-")
        .replaceAll("^-+", "")
        .replaceAll("-+$", "");
    }
}

Option 2:

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public class Solution {
  public static String dashatize(final int number) {
    return String.valueOf(number)
        .replaceAll("([13579])", "-$1-")
        .replaceAll("--", "-")
        .replaceAll("^-|-$", "");
  }
}

Option 3:

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import java.util.*;
public class Solution {
    public static String dashatize(int num) {
    String str = String.valueOf(num);
    if(str.charAt(0) == '-')
      str = str.substring(1);
    return String.join("-",str.split("(?=[1,3,5,7,9])|(?<=[1,3,5,7,9])"));
    } 
}

Test cases to validate our solution

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import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {

    @Test
    public void testBasic() {
        assertEquals("2-7-4", Solution.dashatize(274));
        assertEquals("5-3-1-1", Solution.dashatize(5311));
        assertEquals("86-3-20", Solution.dashatize(86320));
        assertEquals("9-7-4-3-02", Solution.dashatize(974302));
    }

    @Test
    public void testWeird() {
        assertEquals("0", Solution.dashatize(0));
        assertEquals("1", Solution.dashatize(-1));
        assertEquals("28-3-6-9", Solution.dashatize(-28369));
    }
    
    @Test
    public void testEdgeCases() {
        assertEquals("2-1-4-7-48-3-64-7", Solution.dashatize(Integer.MAX_VALUE));
        assertEquals("2-1-4-7-48-3-648", Solution.dashatize(Integer.MIN_VALUE));
        assertEquals("1-1-1-1-1-1-1-1-1-1", Solution.dashatize(-1111111111));
    }
}