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 + '\'' +
'}';
}
}
