Add overflow handling to toDecimal method

Author: mrotteveel

src/main/java/org/firebirdsql/decimal/Decimal.java

@@ -136,6 +136,35 @@ public final <D extends Decimal<D>> D toDecimal(Class<D> decimalType) {
         }
     }
 
+    /**
+     * Converts this decimal to the requested decimal type, rounding when necessary.
+     *
+     * @param decimalType
+     *         Target decimal type
+     * @param overflowHandling
+     *         Handling of overflows
+     * @param <D>
+     *         Type parameter of decimal
+     * @return This value after conversion, or this if {@code decimalType} is the same as this type
+     * @throws IllegalArgumentException
+     *         If conversion to {@code decimalType} is not supported
+     * @throws DecimalOverflowException
+     *         If {@code OverflowHandling#THROW_EXCEPTION} and the value is out of range for the target decimal type.
+     */
+    public final <D extends Decimal<D>> D toDecimal(Class<D> decimalType, OverflowHandling overflowHandling) {
+        if (decimalType == getClass()) {
+            return decimalType.cast(this);
+        } else if (decimalType == Decimal128.class) {
+            return decimalType.cast(Decimal128.valueOf(this, OverflowHandling.THROW_EXCEPTION));
+        } else if (decimalType == Decimal64.class) {
+            return decimalType.cast(Decimal64.valueOf(this, OverflowHandling.THROW_EXCEPTION));
+        } else if (decimalType == Decimal32.class) {
+            return decimalType.cast(Decimal32.valueOf(this, OverflowHandling.THROW_EXCEPTION));
+        } else {
+            throw new IllegalArgumentException("Unsupported conversion to " + decimalType.getName());
+        }
+    }
+
     final DecimalType getType() {
         return type;
     }

src/test/java/org/firebirdsql/decimal/Decimal128Test.java

@@ -245,13 +245,45 @@ public void toDecimal_Decimal128_Decimal32() {
         assertEquals(Decimal32.valueOf("1.23456"), value.toDecimal(Decimal32.class));
     }
 
+    @Test
+    public void toDecimal_Decimal128_Decimal32_valueOutOfRange_toInfinity() {
+        Decimal128 value = Decimal128.valueOf("1.23456E97");
+
+        assertSame(Decimal32.POSITIVE_INFINITY, value.toDecimal(Decimal32.class));
+    }
+
+    @Test
+    public void toDecimal_Decimal128_Decimal32_valueOutOfRange_throwException() {
+        expectedException.expect(DecimalOverflowException.class);
+        expectedException.expectMessage("The scale -92 is out of range for this type");
+        Decimal128 value = Decimal128.valueOf("1.23456E97");
+
+        value.toDecimal(Decimal32.class, OverflowHandling.THROW_EXCEPTION);
+    }
+
     @Test
     public void toDecimal_Decimal128_Decimal64() {
         Decimal128 value = Decimal128.valueOf("1.23456");
 
         assertEquals(Decimal64.valueOf("1.23456"), value.toDecimal(Decimal64.class));
     }
 
+    @Test
+    public void toDecimal_Decimal128_Decimal64_valueOutOfRange_toInfinity() {
+        Decimal128 value = Decimal128.valueOf("1.23456E385");
+
+        assertSame(Decimal32.POSITIVE_INFINITY, value.toDecimal(Decimal32.class));
+    }
+
+    @Test
+    public void toDecimal_Decimal128_Decimal64_valueOutOfRange_throwException() {
+        expectedException.expect(DecimalOverflowException.class);
+        expectedException.expectMessage("The scale -380 is out of range for this type");
+        Decimal128 value = Decimal128.valueOf("1.23456E385");
+
+        value.toDecimal(Decimal32.class, OverflowHandling.THROW_EXCEPTION);
+    }
+
     @Test
     public void validateConstant_POSITIVE_ZERO() {
         assertEquals(BigDecimal.ZERO, POSITIVE_ZERO.toBigDecimal());

src/test/java/org/firebirdsql/decimal/Decimal64Test.java

@@ -253,6 +253,22 @@ public void toDecimal_Decimal64_Decimal32() {
         assertEquals(Decimal32.valueOf("1.23456"), value.toDecimal(Decimal32.class));
     }
 
+    @Test
+    public void toDecimal_Decimal64_Decimal32_valueOutOfRange_toInfinity() {
+        Decimal64 value = Decimal64.valueOf("1.23456E97");
+
+        assertSame(Decimal32.POSITIVE_INFINITY, value.toDecimal(Decimal32.class));
+    }
+
+    @Test
+    public void toDecimal_Decimal64_Decimal32_valueOutOfRange_throwException() {
+        expectedException.expect(DecimalOverflowException.class);
+        expectedException.expectMessage("The scale -92 is out of range for this type");
+        Decimal64 value = Decimal64.valueOf("1.23456E97");
+
+        value.toDecimal(Decimal32.class, OverflowHandling.THROW_EXCEPTION);
+    }
+
     @Test
     public void toDecimal_Decimal64_Decimal128() {
         Decimal64 value = Decimal64.valueOf("1.23456");