Java8 - stream

Java8の変更点の目玉の一つがstreamである．今までのfor文よりもずっときれいにデータプロセス用のコードが書けるようになる．

以下の例は，とある場外取引システムにおけるトレードデータから以下の条件を満たすものを抽出した例．

• TradeDateが2013年１月１日以降
• アクション名がADD
• 取引相手先国が日本

package org.tanuneko.sample;

import java.time.ZonedDateTime;
import java.util.ArrayList;
import java.util.List;

public class StreamSample {

    private static List<Trade> trades = populateTrades();
    private static List<CounterParty> cps = populateCPs();

    private static List<Trade> populateTrades() {
        List<Trade> list = new ArrayList<Trade>();
        list.add( new Trade( "TRD111.1", 1, "ADD", parse( "2013-01-20" ), 1001, true, "15000000ABC" ) );
        list.add( new Trade( "TRD123.1", 1, "ADD", parse( "2013-01-20" ), 1006, true, "16000000ABC" ) );
        list.add( new Trade( "TRD123.1", 2, "MOD", parse( "2013-01-26" ), 1006, true, "16000000ABC" ) );
        list.add( new Trade( "TRD145.1", 1, "ADD", parse( "2013-09-20" ), 1009, true, "T7000000ABC" ) );
        list.add( new Trade( "TRD133.1", 1, "ADD", parse( "2013-06-20" ), 1001, true, "16600000ABC" ) );
        list.add( new Trade( "TRD080.1", 1, "ADD", parse( "2010-07-20" ), 1001, true, "TRD080.1" ) );
        list.add( new Trade( "TRD092.1", 1, "ADD", parse( "2010-09-15" ), 1008, true, "TRD092.1" ) );
        list.add( new Trade( "TRD092.1", 2, "MOD", parse( "2010-09-30" ), 1020, true, "TRD092.1" ) );
        return list;
    }

    private static List<CounterParty> populateCPs() {
        List<CounterParty> cps = new ArrayList<CounterParty>();
        cps.add( new CounterParty( 1001, "US" ) );
        cps.add( new CounterParty( 1009, "Ireland" ) );
        cps.add( new CounterParty( 1006, "Japan" ) );
        cps.add( new CounterParty( 1020, "India" ) );
        cps.add( new CounterParty( 1008, "France" ) );
        cps.sort((l,r) -> l.getCounterPartyId() - r.getCounterPartyId()  );
        return cps;
    }

    private static ZonedDateTime parse( String date ) {
        return ZonedDateTime.parse( date + "T00:00:00-05:00[America/New_York]" );
    }

    public static void main( String args[] ) {
        
        trades.stream()
                .filter(t -> t.getTradeDate().isAfter(parse("2013-01-01")))
                .filter(t -> t.getActionName().equals("ADD") )
                .filter(t -> cps.stream().anyMatch( x -> x.getCounterPartyId() == t.getCounterPartyId() && x.getCountry().equals( "Japan" ) ) )
                .forEach(t -> System.out.println(t));
        cps.forEach( c -> System.out.println( c ) );
    }
}

class CounterParty {

    private int counterPartyId;
    private String country;

    CounterParty(int counterPartyId, String country) {
        this.counterPartyId = counterPartyId;
        this.country = country;
    }

    public int getCounterPartyId() {
        return counterPartyId;
    }

    public String getCountry() {
        return country;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        CounterParty that = (CounterParty) o;

        if (counterPartyId != that.counterPartyId) return false;

        return true;
    }

    @Override
    public int hashCode() {
        return counterPartyId;
    }

    @Override
    public String toString() {
        return "CounterParty{" +
                "counterPartyId=" + counterPartyId +
                ", country='" + country + '\'' +
                '}';
    }
}

class Trade {

    private String tradeId;
    private int eventId;
    private String actionName;
    private ZonedDateTime tradeDate;
    private int counterPartyId;
    private boolean isSDREligible;
    private String USI;

    public Trade( String tradeId, int eventId, String actionName, ZonedDateTime tradeDate,
                   int counterPartyId, boolean isSDREligible, String USI ) {
        this.tradeId = tradeId;
        this.eventId = eventId;
        this.actionName = actionName;
        this.tradeDate = tradeDate;
        this.counterPartyId = counterPartyId;
        this.isSDREligible = isSDREligible;
        this.USI = USI;
    }

    public String getTradeId() {
        return tradeId;
    }

    public int getEventId() {
        return eventId;
    }

    public String getActionName() {
        return actionName;
    }

    public ZonedDateTime getTradeDate() {
        return tradeDate;
    }

    public int getCounterPartyId() {
        return counterPartyId;
    }

    public boolean isSDREligible() {
        return isSDREligible;
    }

    public String getUSI() {
        return USI;
    }

    @Override
    public String toString() {
        return "Trade{" +
                "tradeId='" + tradeId + '\'' +
                ", eventId=" + eventId +
                ", actionName='" + actionName + '\'' +
                ", tradeDate=" + tradeDate +
                ", counterPartyId=" + counterPartyId +
                ", isSDREligible=" + isSDREligible +
                ", USI='" + USI + '\'' +
                '}';
    }
}