Century From Year in Java

The challenge

The first century spans from the year 1 up to and including the year 100The second – from the year 101 up to and including the year 200, etc.

Task :

Given a year, return the century it is in.

Input, Output Examples

centuryFromYear(1705)  returns (18)
centuryFromYear(1900)  returns (19)
centuryFromYear(1601)  returns (17)
centuryFromYear(2000)  returns (20)

The solution in Java code

Option 1:

public class Solution {
  public static int century(int number) {
    return (number + 99) / 100;
  }
}

Option 2:

import java.lang.Math;

public class Solution {
    public static int century(int number) {
        return (int)Math.ceil((double)number/100);
    }
}

Option 3:

public class Solution {
  public static int century(int number) {
    int yearsInCentury = 100;
    return number % yearsInCentury == 0 
      ? number/yearsInCentury 
      : number/yearsInCentury + 1;
  }
}

Option 4:

public class Solution {
  public static int century(int number) {
    int century = (int) number / 100;
    int remains = (int) number % 100;
    if (remains > 0) {
      century += 1;
    }
    return century;
    
  }
}

Test cases to validate our solution

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;
import java.util.Random;
public class Tests {
    @Test
    public void FixedTests() {
        assertEquals(18, Solution.century(1705));
        assertEquals(19, Solution.century(1900));
        assertEquals(17, Solution.century(1601));
        assertEquals(20, Solution.century(2000));
        assertEquals(1,  Solution.century(89));
    }
    @Test
    public void RandomTests() {
      Random rand = new Random();
      for(int i = 0; i < 100;) {
        int a = rand.nextInt(++i * 100);
        int b = (int)(--a/100+1);
        assertEquals(b,  Solution.century(++a));
      }
    }
}
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