test: 完善 Numbers#sum(BigInteger...) 的单元测试

`Numbers` 类新增 `parseXxx` 方法用于将字符串转为对应类型的数字，当转换失败时返回默认值。默认值允许为 `null`。

plusone-commons/src/main/java/xyz/zhouxy/plusone/commons/util/Numbers.java

@@ -29,7 +29,9 @@ import javax.annotation.Nullable;
  */
 public class Numbers {
 
+    // ================================
     // #region - sum
+    // ================================
 
     /**
      * 求和
@@ -131,9 +133,13 @@ public class Numbers {
         return BigDecimals.sum(numbers);
     }
 
+    // ================================
     // #endregion
+    // ================================
 
+    // ================================
     // #region - nullToZero
+    // ================================
 
     /**
      * 将 {@code null} 转换为 {@code 0}
@@ -217,7 +223,122 @@ public class Numbers {
         return BigDecimals.nullToZero(val);
     }
 
-    // #endregion
+    // ================================
+    // #endregion - nullToZero
+    // ================================
+
+    // ================================
+    // #region - parse
+    // ================================
+
+    /**
+     * 将字符串转为对应 {@link Short}，转换失败时返回 {@code defaultValue}（允许为 {@code null}）。
+     *
+     * @param str 要转换的字符串
+     * @param defaultValue 默认值
+     * @return 转换结果
+     */
+    @Nullable
+    public static Short parseShort(@Nullable String str, @Nullable Short defaultValue) {
+        if (StringTools.isBlank(str)) {
+            return defaultValue;
+        }
+        try {
+            return Short.parseShort(str);
+        }
+        catch (NumberFormatException ignore) {
+            // ignore
+        }
+        return defaultValue;
+    }
+
+    /**
+     * 将字符串转为 {@link Integer}，转换失败时返回 {@code defaultValue}（允许为 {@code null}）。
+     *
+     * @param str 要转换的字符串
+     * @param defaultValue 默认值
+     * @return 转换结果
+     */
+    @Nullable
+    public static Integer parseInteger(@Nullable String str, @Nullable Integer defaultValue) {
+        if (StringTools.isBlank(str)) {
+            return defaultValue;
+        }
+        try {
+            return Integer.parseInt(str);
+        }
+        catch (NumberFormatException ignore) {
+            // ignore
+        }
+        return defaultValue;
+    }
+
+    /**
+     * 将字符串转为 {@link Long}，转换失败时返回 {@code defaultValue}（允许为 {@code null}）。
+     *
+     * @param str 要转换的字符串
+     * @param defaultValue 默认值
+     * @return 转换结果
+     */
+    @Nullable
+    public static Long parseLong(@Nullable String str, @Nullable Long defaultValue) {
+        if (StringTools.isBlank(str)) {
+            return defaultValue;
+        }
+        try {
+            return Long.parseLong(str);
+        }
+        catch (NumberFormatException ignore) {
+            // ignore
+        }
+        return defaultValue;
+    }
+
+    /**
+     * 将字符串转为 {@link Float}，转换失败时返回 {@code defaultValue}（允许为 {@code null}）。
+     *
+     * @param str 要转换的字符串
+     * @param defaultValue 默认值
+     * @return 转换结果
+     */
+    @Nullable
+    public static Float parseFloat(@Nullable String str, @Nullable Float defaultValue) {
+        if (StringTools.isBlank(str)) {
+            return defaultValue;
+        }
+        try {
+            return Float.parseFloat(str);
+        }
+        catch (NumberFormatException ignore) {
+            // ignore
+        }
+        return defaultValue;
+    }
+
+    /**
+     * 将字符串转为 {@link Double}，转换失败时返回 {@code defaultValue}（允许为 {@code null}）。
+     *
+     * @param str 要转换的字符串
+     * @param defaultValue 默认值
+     * @return 转换结果
+     */
+    @Nullable
+    public static Double parseDouble(@Nullable String str, @Nullable Double defaultValue) {
+        if (StringTools.isBlank(str)) {
+            return defaultValue;
+        }
+        try {
+            return Double.parseDouble(str);
+        }
+        catch (NumberFormatException ignore) {
+            // ignore
+        }
+        return defaultValue;
+    }
+
+    // ================================
+    // #endregion - parse
+    // ================================
 
     private Numbers() {
         throw new IllegalStateException("Utility class");

plusone-commons/src/test/java/xyz/zhouxy/plusone/commons/util/NumbersTests.java

@@ -26,6 +26,7 @@ import java.util.Arrays;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
 public
@@ -68,9 +69,16 @@ class NumbersTests {
 
     @Test
     public void sum_BigIntegerArray_ReturnsCorrectSum() {
-        BigInteger[] numbers = {new BigInteger("1"), new BigInteger("2"), new BigInteger("3")};
+        BigInteger[] numbers = {
+            new BigInteger("1"),
+            new BigInteger("2"),
+            null,
+            new BigInteger("3")
+        };
         BigInteger result = Numbers.sum(numbers);
         assertEquals(new BigInteger("6"), result);
+
+        assertEquals(BigInteger.ZERO, Numbers.sum(new BigInteger[0]));
     }
 
     @Test
@@ -192,6 +200,100 @@ class NumbersTests {
         assertEquals(BigDecimal.ZERO, result);
     }
 
+    /**
+     * Test for {@link Numbers#parseShort(String, Short)}.
+     */
+    @Test
+    public void parseShort() {
+        assertEquals((short) 12345, Numbers.parseShort("12345", (short) 5));
+        assertEquals((short) 5, Numbers.parseShort("1234.5", (short) 5));
+        assertEquals((short) 5, Numbers.parseShort("", (short) 5));
+        assertEquals((short) 5, Numbers.parseShort(null, (short) 5));
+
+        assertEquals((short) 12345, Numbers.parseShort("12345", null));
+        assertNull(Numbers.parseShort("1234.5", null));
+        assertNull(Numbers.parseShort("", null));
+        assertNull(Numbers.parseShort(null, null));
+    }
+
+    /**
+     * Test for {@link Numbers#parseInteger(String, Integer)}.
+     */
+    @Test
+    public void parseInteger() {
+        assertEquals(12345, Numbers.parseInteger("12345", 5));
+        assertEquals(5, Numbers.parseInteger("1234.5", 5));
+        assertEquals(5, Numbers.parseInteger("", 5));
+        assertEquals(5, Numbers.parseInteger(null, 5));
+
+        assertEquals(12345, Numbers.parseInteger("12345", null));
+        assertNull(Numbers.parseInteger("1234.5", null));
+        assertNull(Numbers.parseInteger("", null));
+        assertNull(Numbers.parseInteger(null, null));
+    }
+
+    /**
+     * Test for {@link Numbers#parseLong(String, Long)}.
+     */
+    @Test
+    public void parseLong() {
+        assertEquals(12345L, Numbers.parseLong("12345", 5L));
+        assertEquals(5L, Numbers.parseLong("1234.5", 5L));
+        assertEquals(5L, Numbers.parseLong("", 5L));
+        assertEquals(5L, Numbers.parseLong(null, 5L));
+
+        assertEquals(12345L, Numbers.parseLong("12345", null));
+        assertNull(Numbers.parseLong("1234.5", null));
+        assertNull(Numbers.parseLong("", null));
+        assertNull(Numbers.parseLong(null, null));
+    }
+
+    /**
+     * Test for {@link Numbers#parseFloat(String, Float)}.
+     */
+    @Test
+    public void parseFloat() {
+        assertEquals(1.2345f, Numbers.parseFloat("1.2345", 5.1f));
+        assertEquals(5.0f, Numbers.parseFloat("a", 5.0f));
+        assertEquals(5.0f, Numbers.parseFloat("-001Z.2345", 5.0f));
+        assertEquals(5.0f, Numbers.parseFloat("+001AB.2345", 5.0f));
+        assertEquals(5.0f, Numbers.parseFloat("001Z.2345", 5.0f));
+        assertEquals(5.0f, Numbers.parseFloat("", 5.0f));
+        assertEquals(5.0f, Numbers.parseFloat(null, 5.0f));
+
+        assertEquals(1.2345f, Numbers.parseFloat("1.2345", null));
+        assertNull(Numbers.parseFloat("a", null));
+        assertNull(Numbers.parseFloat("-001Z.2345", null));
+        assertNull(Numbers.parseFloat("+001AB.2345", null));
+        assertNull(Numbers.parseFloat("001Z.2345", null));
+        assertNull(Numbers.parseFloat("", null));
+        assertNull(Numbers.parseFloat(null, null));
+    }
+
+    /**
+     * Test for {@link Numbers#parseDouble(String, Double)}.
+     */
+    @Test
+    public void parseDouble() {
+        assertEquals(1.2345d, Numbers.parseDouble("1.2345", 5.1d));
+        assertEquals(5.0d, Numbers.parseDouble("a", 5.0d));
+        assertEquals(1.2345d, Numbers.parseDouble("001.2345", 5.1d));
+        assertEquals(-1.2345d, Numbers.parseDouble("-001.2345", 5.1d));
+        assertEquals(1.2345d, Numbers.parseDouble("+001.2345", 5.1d));
+        assertEquals(0d, Numbers.parseDouble("000.00", 5.1d));
+        assertEquals(5.1d, Numbers.parseDouble("", 5.1d));
+        assertEquals(5.1d, Numbers.parseDouble((String) null, 5.1d));
+
+        assertEquals(1.2345d, Numbers.parseDouble("1.2345", null));
+        assertEquals(null, Numbers.parseDouble("a", null));
+        assertEquals(1.2345d, Numbers.parseDouble("001.2345", null));
+        assertEquals(-1.2345d, Numbers.parseDouble("-001.2345", null));
+        assertEquals(1.2345d, Numbers.parseDouble("+001.2345", null));
+        assertEquals(0d, Numbers.parseDouble("000.00", null));
+        assertEquals(null, Numbers.parseDouble("", null));
+        assertEquals(null, Numbers.parseDouble((String) null, null));
+    }
+
     @Test
     void test_constructor_isNotAccessible_ThrowsIllegalStateException() {
         Constructor<?>[] constructors = Numbers.class.getDeclaredConstructors();