Resolve "Java puzzle code"

Closes #104 (closed)

java-puzzles/src/test/java/fr/ippon/PlayingWithBigDecimal.java

+package fr.ippon;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.math.BigDecimal;
+import org.junit.jupiter.api.Test;
+
+public class PlayingWithBigDecimal {
+
+  @Test
+  public void roundingSubstract() {
+    BigDecimal a = new BigDecimal(2.00);
+    BigDecimal b = new BigDecimal(0.99);
+  // assertThat(a.subtract(b).toString()).isEqualTo("1");
+  // assertThat(a.subtract(b).toString()).isEqualTo("1.01");
+  // assertThat(a.subtract(b).toString()).isEqualTo("1.0100000000000000088817841970012523233890533447265625");
+  }
+}