• SUM求和运算函数

public class Sum {//Need an inner class to store data/*required*/public static class State {/*some variables if you need */public BigDecimal sum;}/*required*/public State create() {/* here could do some init work if needed */State state = new State();state.sum = new BigDecimal(0);return state;}/*required*/public void destroy(State state) {/* here could do some destroy work if needed */}/*Not Required*/public void reset(State state) {/*if you want this udaf function can work with window function.*//*Must impl this, it will be reset to init state after calculate every window frame*//**state.sum = new BigDecimal(0);**/}/*required*///first argument is State, then other types your inputpublic void add(State state, String value) throws Exception {try {/* here doing update work when input data*/if (null != value && !"".equals(value)) {state.sum = state.sum.add(new BigDecimal(value));}} catch (Exception e) {log.info(e.getMessage());}}/*required*/public void serialize(State state, DataOutputStream out)  {/* serialize some data into buffer */try {out.writeUTF(state.sum.toString());} catch (Exception e) {/* Do not throw exceptions */log.info(e.getMessage());}}/*required*/public void deserialize(State state, DataInputStream in)  {/* deserialize get data from buffer before you put */String value = "0";try {value = in.readUTF();} catch (Exception e) {/* Do not throw exceptions */log.info(e.getMessage());}state.sum = new BigDecimal(value);}/*required*/