BigDecimal adding wrong value

Use a String literal:

private static final BigDecimal sd = new BigDecimal("0.7");

If you use a double, actually public BigDecimal(double val) is called. The reason you do not get 0.7 is that it cannot be exactly represented by a double. See the linked JavaDoc for more information.

Perhaps if you bothered to read the documentation, i.e. the javadoc of the constructor you're using, you'd already know the answer.

3. When a double must be used as a source for a BigDecimal, note that this constructor provides an exact conversion; it does not give the same result as converting the double to a String using the Double.toString(double) method and then using the BigDecimal(String) constructor. To get that result, use the static valueOf(double) method.

When you then look at the javadoc of BigDecimal.valueOf(double), you'll find:

Note: This is generally the preferred way to convert a double (or float) into a BigDecimal, as the value returned is equal to that resulting from constructing a BigDecimal from the result of using Double.toString(double).

So there is your answer: Use BigDecimal.valueOf(0.7d), not new BigDecimal(0.7d).