Performance Recommendations - General Programming

Recommendation

The CrEme virtual machine uses more resources for emory allocation and object instantiation than the Win32 standard Sun VM.

The following example shows an unnecessary instantiation:

// set quantity to sales order item
  if ((quantity != null) && !("".equals(quantity)))            {
    salesOrderItem.setReqQty(new FixedDecimal(quantity, 14, 3));
  } else {
    salesOrderItem.setReqQty(new FixedDecimal("0", 14, 3));
  }

Reason:

If the quantity value is not set, a constant quantity of 0 (represented as a FixedDecimal) will be assigned. The FixedDecimal object is not defined as a constant so it will be instantiated every time. This is resource consuming, especially with a FixedDecimal object.

Solution:

Define constant values as constants (final static) and try to instantiate objects once and reuse them as often as possible. However, excessive saving of objects can have a negative affect on the memory consumption.

Concatenation of more than 2 Strings with the + Operator in frequently called methods is very resource consuming. This is a general Java issue. When concatenating Strings with + a new String Object is instantiated, together with memory-allocation for the underlying char array, for every single concatenation.

Example: Following command instantiates 9 objects and allocates char-arrays.

String s = “hello ” + “world ” + “here ” + “I “ + “am “; 

Example: Ineffective way to a add trailing spaces.

private String addLeadingSpaces(String st, int len)
{
  while (st.length() < len)
  {
    st = "0"+ st;
  }
  return st;
}