feat: add test case

src/main/java/me/hatter/math/Sqrt10.java

@@ -23,10 +23,10 @@ public class Sqrt10 {
     //    }
     //}
     public static BigDecimal sqrt10() {
-        BigDecimal x = BigDecimal.valueOf(1).divide(BigDecimal.valueOf(6), 100, RoundingMode.FLOOR);
+        BigDecimal x = BigDecimal.valueOf(1).divide(BigDecimal.valueOf(6), 100, RoundingMode.HALF_UP);
 
         for (int i = 0; i < 100; i++) {
-            x = BigDecimal.valueOf(1).divide(BigDecimal.valueOf(6).add(x), 100, RoundingMode.FLOOR);
+            x = BigDecimal.valueOf(1).divide(BigDecimal.valueOf(6).add(x), 100, RoundingMode.HALF_UP);
         }
 
         return BigDecimal.valueOf(3).add(x);

src/main/java/me/hatter/math/util/MathUtil.java

@@ -35,9 +35,13 @@ public class MathUtil {
     }
 
     public static BigDecimal simpleContinuedFraction(long[] nums) {
+        return simpleContinuedFraction(nums, 100);
+    }
+
+    public static BigDecimal simpleContinuedFraction(long[] nums, int scale) {
         BigDecimal v = BigDecimal.ZERO;
         for (int i = nums.length - 1; i > 0; i--) {
-            v = BigDecimal.ONE.divide(v.add(BigDecimal.valueOf(nums[i])), 100, RoundingMode.FLOOR);
+            v = BigDecimal.ONE.divide(v.add(BigDecimal.valueOf(nums[i])), scale, RoundingMode.HALF_UP);
         }
         return v.add(BigDecimal.valueOf(nums[0]));
     }
@@ -52,15 +56,15 @@ public class MathUtil {
             return BigDecimal.ZERO;
         }
 
-        BigDecimal x = n.divide(new BigDecimal("2"), scale, RoundingMode.HALF_UP);
+        BigDecimal x = n.divide(BigDecimal.valueOf(2), scale, RoundingMode.HALF_UP);
-        BigDecimal precision = new BigDecimal("1").movePointLeft(scale); // 誤差の許容範囲
+        BigDecimal precision = BigDecimal.ONE.movePointLeft(scale); // 誤差の許容範囲
         BigDecimal lastX;
 
         do {
             lastX = x;
             x = n.divide(x, scale, RoundingMode.HALF_UP)
                     .add(x)
-                    .divide(new BigDecimal("2"), scale, RoundingMode.HALF_UP);
+                    .divide(BigDecimal.valueOf(2), scale, RoundingMode.HALF_UP);
         } while (x.subtract(lastX).abs().compareTo(precision) > 0);
 
         return x;

src/test/java/me/hatter/math/util/MathUtilTest.java

@@ -4,6 +4,7 @@ import org.junit.Assert;
 import org.junit.Test;
 
 import java.math.BigDecimal;
+import java.math.RoundingMode;
 
 public class MathUtilTest {
 
@@ -45,4 +46,24 @@ public class MathUtilTest {
                 MathUtil.simpleContinuedFraction(new long[]{3, 7, 16, 1, 3, 4, 2, 3, 1})
         ));
     }
+
+    @Test
+    public void testSqrt() {
+        Assert.assertEquals(
+                new BigDecimal("3.1622776601683793319988935444327185337195551393252168268575048527925944386392382213442481083793002952"),
+                MathUtil.sqrt(BigDecimal.valueOf(10), 100)
+        );
+        Assert.assertEquals(
+                MathUtil.simpleContinuedFraction(new long[]{1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+                        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+                        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+                        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2}),
+                MathUtil.sqrt(BigDecimal.valueOf(2), 110).setScale(100, RoundingMode.HALF_UP)
+        );
+        Assert.assertEquals(
+                MathUtil.simpleContinuedFraction(new long[]{3, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+                        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6}),
+                MathUtil.sqrt(BigDecimal.valueOf(10), 100)
+        );
+    }
 }