package net.sf.jasperreports.engine.fill;

class JRIntegerSumIncrementer extends JRAbstractExtendedIncrementer {
  private static JRIntegerSumIncrementer mainInstance = new JRIntegerSumIncrementer();
  
  public static JRIntegerSumIncrementer getInstance() {
    return mainInstance;
  }
  
  public Object increment(JRCalculable variable, Object expressionValue, AbstractValueProvider valueProvider) {
    Number value = (Number)variable.getIncrementedValue();
    Number newValue = (Number)expressionValue;
    if (newValue == null) {
      if (variable.isInitialized())
        return null; 
      return value;
    } 
    if (value == null || variable.isInitialized())
      value = JRIntegerIncrementerFactory.ZERO; 
    return new Integer(value.intValue() + newValue.intValue());
  }
  
  public Object initialValue() {
    return JRIntegerIncrementerFactory.ZERO;
  }
}