Java

1
?????????????? ???????????????? ? Java

• ??????? ????????
• ekirpichov_at_gmail.com
• 2008

2
????

• ?????????
• ????????? ??????????
• ????????? ? ????????? ??
• ???????

3
?????????? Java

• ????
• ???????????? ????? ????? (???????? ?????????????)
• ?????????? ?????????? ??? ???????/????????/???????
  ?/
• ??????? ????????? ??? ????????? (?????????
  ???????)
• ?????????? ???????? ? ?.?.
• ????????
• Kingdom of nouns
• new NumberAdder(new IntegerValue(2), new
  IntegerValue(2)).performOperation()
• Boilerplate is OK, ??? ?? Java

4
??? ?? ?? ???????

• ????????
• ??????????? ???????
• ?????-???????, ? ????? ?????
• ????????? ?????? ? ???????? ????????
• ?????? SICP
• Abelson, Sussman Structure and Interpretation
  of Computer Programs
• ???? ?? ??????? ???????? ? ???????????
• ???????? ??????????? ?????

5
????

• ?????????
• ????????? ??????????
• ????????? ? ????????? ??
• ???????

6
????????? ??????????

• Generics / type inference
• ???????? ??????
• ???????? ????????
• Naming conventions
• ? ??????

7
????????? ?????????? Generics

• MapltInteger, ListltStringgtgt namesById new
  HashMapltInteger, ListltStringgtgt()
• ListltPairltFoo,Bargtgt foosAndBars new
  ArrayListltPairltFoo,Bargtgt()
• MapltString, MapltString,Stringgtgt thingsByName
• new LinkedHashMapltString, MapltString,Stringgtgt().

?????? ?? ?? MapltInteger, ListltStringgtgt
namesById new HashMap() ListltPairltFoo,Bargtgt
foosAndBars new ArrayList() MapltString,
MapltString,Stringgtgt thingsByName new
LinkedHashMap() ?????? ??? ???????? raw-????, ?
?? ??, ??? ?????. ??? ????????????? ????? ?????
??????, ???? ??? ??????? ??? ???? ?? ???. ???
???? ?? ???????????? ???? ????????
8
????????? ?????????? Generics

• ??? ???? ?? ???????????? ???? ????????
• public class CollectionFactory
• public static ltK,Vgt MapltK,Vgt
  newUnorderedMap()
• return new HashMapltK,Vgt()
• public static ltAgt ListltAgt newList()
• return new ArrayListltAgt()
• import static CollectionFactory.
• MapltInteger, ListltStringgtgt namesById
  newUnorderedMap()
• ListltPairltFoo,Bargtgt foosAndBars newList()

9
????????? ?????????? ???????? ??????

• ???????
• compressImages(Image.JPEG, new String
  foo.jpg, bar.jpg, baz.jpg)
• ?????????
• private static final SetltStringgt FORBIDDEN_TAGS
  newUnorderedSet()
• static
• FORBIDDEN_TAGS.add(SCRIPT)
• FORBIDDEN_TAGS.add(INPUT)
• FORBIDDEN_TAGS.add(LINK)
• ???????
• MapltString,Stringgt params newLinkedMap()
• params.put(product_id, productId)
• params.put(action, get_price)
• params.put(historyLen, 5)
• request new HttpPOST(http//www.site.com/main.h
  tml, params)

10
????????? ?????????? ???????? ??????

• public class CollectionFactory
• public static ltTgt T array(T ts)
  return ts
• public static ltTgt ListltTgt listOf(T ts)
  return Arrays.asList(ts)
• public static ltTgt SetltTgt setOf(T ts)
  return newUnorderedSet(ts)
• /
• kvs is like key,value, key,value,
• /
• public static ltK,Vgt MapltK,Vgt mapOf(Object
  kvs)

11
????????? ?????????? ???????? ??????

• ???????
• compressImages(Image.JPEG, array(foo.jpg,
  bar.jpg, baz.jpg))
• ?????????
• private static final SetltStringgt FORBIDDEN_TAGS
  setOf(SCRIPT,LINK,INPUT)
• ???????
• request new HttpPOST(http//www.site.com/main.h
  tml,
• mapOf(product_id, productId,
• action, get_price,
• historyLen, 5))
• ??????
• import static is a good thing.
• varargs are a good thing.

12
????????? ?????????? ???????? ??????

• ???????????? ?????????? ??????????? DSL
• _at_Test
• public void testIsConnected()
• assertTrue (GraphAnalyzer.isConnected(graph(1
  -gt2 2-gt3 3-gt1)))
• assertFalse(GraphAnalyzer.isConnected(graph(1
  -gt2 2-gt1 3-gt4)))
• private static Graph graph(String representation)
  
• // ?????? ?????????? ? ????? ?? ??????
  ???????

13
???????????? vs. ?????????? ???

• private static Graph graph(String
  representation)
• // ?????? ?????????? ? ????? ?? ??????
  ???????
• ??????????
• ?????????? ???
• ?????????? ?????????? ? ????????????
• ???????????? ???
• ?????????? ? ???????????? ??? ?????????????
• ?????????? ?????????? ? ???????????? ???????????
  ????

14
????????? ?????????? ???????? ????????

• ?????? ????????????? ?? static factory method.
• Filter f new AndFilter(first, second)
• searchConditions.add(new FieldCondition(title,
• new StringCondition(Jjava",
• StringComparisonKind.REGEX,
• StringPosition.ANYWHERE))
• document.append(
• new Element(image, array(
• new Attribute(url, ), new
  Attribute(title, ))))
• ?? ??? ?? ? ?????, ?? ???? ?????? ?????!

15
????????? ?????????? ???????? ????????

• ?????? ????????????? ?? static factory method.
• import static com.acme.util.Filters.
• Filter f and(first, second)
• import static com.acme.search.Conditions.
• searchConditions.add(onField(title,
  regexAnywhere(Jjava))
• import static com.acme.document.Elements.
• document.append(image(url(), title())
• ????????????
• ??? ??????, ?????? ??????
• ??????, ? ??????? ?? ?????????????, ?????
  ????????
• regexAnywhere, regexWhole, exactMatchAnywhere,
  exactMatchWhole
• vs
• new StringCondition(Jjava",

16
????????? ?????????? ?????????? ???????

• ????????? ??????? ????? ????? ????????
• ListltCustomergt customers map(orders, new
  FunctionltOrder,Customergt()
• public Customer apply(Order arg)
• return arg.getCustomer()
• )
• ??-??????, ?? ???? ?????????, ???? ??????
  ????????, ??? map/fold.
• ListltCustomergt customers newList()
• for(Order ord orders)
• customers.add(ord.getCustomer())

17
????????? ?????????? ?????????? ???????

• ?? ???? ?? ? ???????????? ????????? ?????, ??
  ????? ???
• private static final FunctionltOrder,Customergt
  GET_CUSTOMER new FunctionltOrder,Customergt()
• public Customer apply(Order arg)
• return arg.getCustomer()
• ListltCustomergt customers map(GET_CUSTOMER,
  orders)
• ??? ???????, ????
• ?????????? ??? ?????? ? ????????
• ? ???????? ????????? ????????????
• GET_CUSTOMER ????? ??????????? ??? ???.
• ?????????? ??? ????? ??????? ????????? ?
  ???????????? ???.

18
????????? ?????????? ?????????? ???????

• ?????????? ??????????? ???????
• StringCondition regex new RegexStringCondition()
  
• CustomerProcessor taxes new ComputeTaxesCustomer
  Processor()
• WindowEventListener listener new
  CaptureDoubleClicksWindowEventListener()
• WTF?
• ??? ???????? ?? ?????.
• StringCondition regex new Regex()
• CustomerProcessor taxes new ComputeTaxes()
• WindowEventListener listener new
  CaptureDoubleClicks()
• ???????????? ???????? ????????? ????, ?? ???
  ????? ???????? package???, ? ???????? ??
  ????????? ?????? ????, ??? ??????? ? ????.

19
????????? ?????????? ?????????? ???????

• class Type
• public boolean isParent(Type other)
• ??? ?????? this.isParent(other) ? ????????
  other ??? ??? ???????? - other?
• class DNASequence
• public int index(DNASequence other)
• class KungFu
• public boolean isBetter(KungFu yours)
• ?? ?? ???????.

20
????????? ?????????? ?????????? ???????

• class Type
• public boolean isParentOf(Type other)
• ???
• public boolean isChildOf(Type other)
• class DNASequence
• public int indexOf(DNASequence other)
• ???
• public int indexIn(DNASequence other)
• (????????, ??? ? ???????
  ?????-???????????? ???????????)
• class KungFu
• public boolean isBetterThan(KungFu yours)

21
????????? ?????????? ?????????? ???????

• ????? ???????
• ???? relates ???????? ????????? ?????????, ??
  x.relates(y) ?????? ???????? ?????????? ??? x
  relates y.
• ???? op ???????? ????????? ???????? ????????, ??
  x.op(y) ?????? ???????? ???? ?????????? ??? x op
  y, ???? ??? x, give me op(y)
• Mary is parent John ????????????
• Mary is parent of John ??????????
• My kung fu is better yours ????????????
• My kung fu is better than yours - ??????????
• accel multiply dt ????????????
• accel multiplied by dt ??????????
• accel times dt ??????????
• genome index AGCTG ????????????
• genome, give me index of AGCTG - ??????????

22
????????? ?????????? ?????????? ??????????

• ???????, ?????? ???, ?????????????.
• ???????? ??????? ?? ????
• MapltLong,Stringgt categories
• MapltLogEntry, ListltLogDescrgtgt fooLog
• MapltLogEntry, ListltLogDescrgtgt entries
• MultiMapltString,Stringgt siteGraph
• ?????????
• public class BarMapper
• private final MapltLong, Longgt bars new
  HashMapltLong, Longgt()
• public void setBars(MapltLong, Longgt bars)
• this.bars.putAll(bars)
• public MapltLong, Longgt getBars()

23
????????? ?????????? ?????????? ??????????

• ???????, ?????? ???, ?????????????.
• MapltLong,Stringgt categoryId_Name
• MapltLogEntry, ListltLogDescrgtgt entry_bars
• MultiMapltString,Stringgt url_outLink
• public class BarMapper
• private final MapltLong, Longgt old_newBarId
  newUnorderedMap()
• public void setOld_NewBarId(MapltLong, Longgt
  old_newBarId)
• this.old_newBarId.putAll(old_newBarId)
• public SetltLonggt getOldBarIds()
• return old_newBarId.keySet()

24
????

• ?????????
• ????????? ??????????
• ????????? ? ????????? ??
• ???????

25
????????? ? ????????? ??

• ??????? ?????????? ?????????
• ??????? ? ?????????
• ??????? ???????????

26
????????? ? ????????? ????????? ??????????
?????????

• ??? ???????????? filter(), map(), fold()?
• ListltFoogt foos map(GET_FOO, bars)
• ListltProductgt expensive filter(priceMoreThan(100
  ), products)
• ????????? ??? ???????????? ?????????????
• ?? ????????? ??????????????
• ??? ????? ??? ????? command-line ?????????,
  ??????? ????? ???????? ?????? ? ???????, ? ?? ?
  stdin/stdout ?????? ??????? ? ????????
  ???????????? ?????????
• cat file.txt grep foo sed s/foo/bar/ sort
  uniq c sort n
• ??????????????? ?????
• vs
• grep foo file.txt gt tmp1.txt
• sed s/foo/bar/ tmp1.txt gt tmp2.txt
• sort tmp2.txt gt tmp3.txt
• uniq c tmp3.txt gt tmp4.txt
• sort n tmp4.txt gt tmp5.txt
• cat tmp5.txt

27
????????? ? ????????? ????????? ??????????
?????????

• ?????? ?????? ?????????????? map(GET_FOO, _)
  ??? filter(priceMoreThan(100), _).
• ???????
• ???????????? ????????
• ????? ??????????? ?? ??????????, ? ?????????
• sort Options -gt stdin -gt stdout
• sort n stdin -gt stdout ???????? ??? ???????
• vs
• sort Options -gt FileName -gt stdout
• sort n file.txt stdout
• public static ltK,Vgt FunctionltListltKgt,ListltVgtgt map
  (FunctionltK,Vgt f)
• public static ltKgt FunctionltListltKgt,ListltKgtgt
  filter(FilterltKgt f)
• vs
• public static ltK,Vgt ListltVgt map (FunctionltK,Vgt
  f, ListltKgt ks)
• public static ltKgt ListltKgt filter(FilterltKgt f,
  ListltKgt ks)

28
????????? ? ????????? ????????? ??????????
?????????

• public static ltK,Vgt FunctionltListltKgt,ListltVgtgt
  map(FunctionltK,Vgt f)
• public static ltK,Vgt FunctionltListltKgt,ListltKgtgt
  filter(FilterltKgt f)
• public abstract class FunctionltK,Vgt
• public abstract V apply(K argument)
• public final FunctionltK,Ugt then(FunctionltV,Ugt
  second)
• public class CollectionUtils
• public static ltV extends Comparablelt? super
  Vgtgt
• FunctionltIterableltKgt, Kgt
  maximizeBy(FunctionltK,Vgt byWhat)
• public static ltKgt
• FunctionltIterableltKgt, Vgt
  over(FunctionltK,Booleangt filter,
  FunctionltIterableltKgt, Vgt fun)

29
????????? ? ????????? ????????? ??????????
?????????

• ????? Order (Customer, Product, Time)
• FunctionltOrder,Customergt ORDER_CUSTOMER
• FunctionltOrder,Productgt ORDER_PRODUCT
• FunctionltProduct,Pricegt PRODUCT_PRICE
• FilterltProductgt categoryEquals(String pattern)
  ..
• // select month, agg(order) from orders group by
  month
• PartitionedltOrder,Month,Tgt byMonth(AggregateltOrder
  , Tgt agg) ..
• public PartitionedltOrder,Month,Customergt
  mostGenerousCustomerByMonth()
• FunctionltOrder, Pricegt ORDER_PRICE
  ORDER_PRODUCT.then(ORDER_PRICE)
• AggregateltOrder, Ordergt MOST_EXPENSIVE_ORDER
  
• over(ORDER_PRODUCT.then(categoryEquals("Ca
  rs")),
• maximizeBy(ORDER_PRICE))
• return byMonth(MOST_EXPENSIVE_ORDER.then(ORDER
  _CUSTOMER))

30
????????? ? ????????? ????????? ? ?????????

• ?????? ????? ??????????? ?????????? ???? ? ??????
• ? ????? ?? ??????
• ? ??????? ?? ?? ?????????
• ??? ????????????? ???????
• ????? ???????? ??? ???? ??? ? ??? ???????

31
????????? ? ????????? ????????? ? ?????????

• ? ????? ??????? ?????
• ?????? ??? ????? ???????? ?? ???????? ?????????
• class BiRelationltL,Rgt
• ListltPairltL,Rgtgt allEntries()
  
  
• static BiRelationltL,Rgt rel(ListltPairltL,Rgtgt
  pairs)
  
• BiRelationltR,Lgt flip()
  
  
• BiRelationltL,Rgt filterL(PredicateltLgt p)
  
  
• BiRelationltR,Lgt filterR(PredicateltRgt p)
  return flip().filterL(p).flip()
  
• BiRelationltL,ListltRgtgt compressL()
  
  
• BiRelationltListltLgt,Rgt compressR()
  return flip().compressL().flip()
  

32
????????? ? ????????? ????????? ? ?????????

• ????? ? ??????
• private static BiRelationltNode, Nodegt
  bfs(BiRelationltNode, Nodegt graph, Node root)
• SetltNodegt roots singleton(root)
• SetltNodegt reached new
  LinkedHashSetltNodegt()
• reached.add(root)
• ListltPairltNode,Nodegtgt res newList()
• while(true)
• BiRelationltNode,Nodegt nextLayer
• graph.filterL(memberOf(roots)).f
  ilterR(not(memberOf(reached)))
• if(nextLayer.isEmpty())
• break
• res.addAll(nextLayer.allEntries())
• reached.addAll(roots
  nextLayer.rightSet())
• return rel(res)

33
????????? ? ????????? ????????? ? ?????????

• ?????????????? ??????
• ?????????? ??????? ?? ???????? ???????
• ??????? ????? ??????? ??????????? ????????? ??
  O(N log N) ???
• ???????? ?? ?? ???? ????????? ?? O(N), ?????
  ???????????, ????? ??????
• public static FunctionltT, PairltT,Ugtgt
  attachR(FunctionltT,Ugt fun) ..
• public static FunctionltPairltT,Ugt, Tgt detachR()
  ..
• public static FunctionltPairltT,Ugt, Ugt detachL()
  ..
• public static ltU extends Comparablelt? super Ugtgt
• FunctionltListltTgt,ListltTgtgt sortBy(FunctionltT,Ugt
  fun)
• public static ltU extends Comparablelt? super Ugtgt
• FunctionltListltTgt,ListltTgtgt schwartzSortBy(Funct
  ionltT,Ugt fun)
• return map(attachR(fun)).then(sortBy(second())
  ).then(map(detachR()))

34
????????? ? ????????? ????????? ???????????

• ??????? ??????? ?? map,filter,fold ???
  ???????????? ????? ????????????? ???????
• ???????? ???????? ?? GC
• ? ???????? ?????? ???, ?.?. ?????? ???????
• ??? ???????, ?? ????? ?????
• AggregateltCustomer, Ordergt everyonesOrdersIn2008
  map(GET_ORDERS).then(concat()).then(filter(timeB
  etween(year(2007), year(2008))))
• ??????????? ??????????? VLIW (Very Large
  Instruction Word)
• ???? ?????????? ????? ????????? ????????
• ??????????? ? ??????? ? ?????????????
• ????????? sin ? cos
• ??????? ??? ??
• public static ltK,Vgt AggregateltK,Vgt
  concatMapOver(FunctionltK,Vgt fun, FilterltKgt
  filter)
• AggregateltCustomer, Ordergt everyonesOrdersIn2008
  
• concatMapOver(GET_ORDERS, timeBetween(year(200
  7), year(2008)))
• ??? ????? ??????????? ??????? ???????????, ???
  ????????????? ???????

35
???????

• JDBC ?????? ? ?????? ??????
• ???????? ????????? ??????, ??????????,
  ????????????? ? ?.?.

36
JDBC

• ListltTgt query(sql, RowMapperltTgt)
• ListltIntegergt foos db.query("select id from foo
  where is_nice 1",
• new RowMapperltIntegergt()
• public Integer mapRow(ResultSet rs, int
  rownum)
• return rs.getInt(1)
• )
• void query(sql, RowCallbackltTgt)
• MapltInteger,Stringgt id_name newUnorderedMap()
• db.query("select id, name from foo where
  is_nice1",
• new RowCallbackHandler()
• void handleRow(ResultSet rs, int rownum)
  
• id_name.put(rs.getInt(1),
  rs.getString(2))
• )

37
JDBC

• 80 ???? ?????
• ?????? ????? ????? ???????????
• ? ?????? ?????????? 95.3 ???? ?????

38
JDBC

• public class RowMappers
• public static RowMapperltIntegergt getInt(final
  int i)
• return new RowMapperltIntegergt()
• public Integer mapRow(ResultSet rs,
  int rownum)
• return rs.getInt(i)
• public static RowMapperltStringgt
  getString(final int i)
• return new RowMapperlt String gt()
• public String mapRow(ResultSet rs,
  int rownum)
• return rs.getString(i)

39
JDBC

• ??, ??? boilerplate ? ????? 80 ???? - ?????
• ?? boilerplate ????????????
• ??????????
• ?????????? ???
• ?????????? ??????????
• ???????????? ???
• ?????????? ??? ?????????????
• ?????????? ?????????? ??????????? ????

40
JDBC

• ListltIntegergt foos db.query(
• "select id from foo where is_nice 1",
• new RowMapperltIntegergt()
• public Integer mapRow(ResultSet rs, int
  rownum)
• return rs.getInt(1)
• )
• vs
• ListltIntegergt foos db.query(
• "select id from foo where is_nice 1",
• RowMappers.getInt(1))

41
JDBC

• ???????? ?????? SICP
• ???? ????????? ???????? ?????????? ????????
  ??????????
• ????????? ??? ????
• ???????? ?????????? ???? Java (???????????
  ??????????? ??????? ? ???????)
• ???????? ?????????? Here comes the cool part

42
JDBC

• RowMappers ???????? ??????????
• RowMapperltKgt RowMapperltVgt ? RowMapperltPairltK,Vgt
  gt
• RowMapperltKgt FunctionltK,Vgt/MapltK,Vgt ?
  RowMapperltVgt
• RowMapperltIntegergt ListltVgt ? RowMapperltVgt
• ??????? ?????? ???????????
• FunctionltInteger,Vgt indexList(ListltVgt)
• RowMapperltKgt K (??? ??????? ? ?????? null) ?
  RowMapperltKgt
• K.class RowMapper ? RowMapperltKgt (?????
  ????????????)
• RowMapperltKgt simply(K) ??????????? ??????

43
JDBC

• ???? ??????????
• public static ltK,Vgt RowMapperltVgt
  fmap(FunctionltK,Vgt f, RowMapperltKgt keyMapper)
• return new RowMapperltVgt()
• public V mapRow(ResultSet rs, int rownum)
  
• return f.apply(keyMapper.mapRow(rs,row
  num))
• public static ltK,Vgt RowMapperltVgt
  indexMapWith(MapltK,Vgt map, RowMapperltKgt
  keyMapper)
• return fmap(getFromMap(map), keyMapper)

44
JDBC

• ??????
• MapltString,Stringgt synonyms ...
• ListltFoogt foos db.query(
• "select id, name, bar from foo where bar gt
  10",
• constructor(Foo.class,
• integerAt(1),
• nvl(indexMapWith(synonyms, stringAt(2)),
  "unnamed"),
• doubleAt(3)))

45
JDBC

• RowCallbacks ?????????
• ?????? ???????????? ??? ??????????/???????? ?
  ??????? ? ?????????
• addToCollection, removeFromCollection
• RowMapperltKgt CollectionltKgt ? RowCallback
• addToMap
• RowMapperltKgt RowMapperltVgt MapltK,Vgt ?
  RowCallback
• removeFromMap
• RowMapperltKgt MapltK,Vgt ? RowCallback
• ?????????? removeFromCollection(map.keySet())
• ??????????? ??? ??????, ????????
• addToReport(Report)
• printOnWriter(Writer)

46
JDBC

• RowCallbacks ???????? ??????????
• chain ?????????? ???????? ?????????? RowCallback
• RowCallback ? RowCallback
• ifElse ????????? ? ??????????? ?? ????,
  ????????????? ?? ??? ?????????
• RowMapperltBooleangt RowCallback RowCallback ?
  RowCallback
• ???? ?????????????, ????????? ????? ???????, ???
  ????????? ????? ? ???? ??????????? ??????????
• ????? ????????? ?????? ? ??????? ???????

47
JDBC

• ???? ??????????
• public static RowCallback chain(RowCallback...
  parts)
• return new RowCallback()
• public void processRow(ResultSet rs, int
  rownum)
• for(RowCallback p parts)
• p.processRow(rs,rownum)
• public static RowCallback ifElse(
• RowMapperltBooleangt condition, RowCallback
  then, RowCallback otherwise)
• return new RowCallback()
• public void processRow(ResultSet rs, int
  rownum)
• if(Boolean.TRUE condition.mapRow(rs
  ,rownum))
• then.processRow(rs,rownum)
• else

48
JDBC

• ??????
• MapltInteger,Doublegt rich newUnorderedMap(),
  poor newUnorderedMap()
• db.query(
• "select id, salary, (case when salary gt 100
  then 1 else 0 end) "
• "from employees",
• ifElse(booleanAt(3),
• addToMap(rich, integerAt(1),
  doubleAt(2)),
• addToMap(poor, integerAt(1),
  doubleAt(2))))

49
?????? ????????

• ?????????
• ????????? ??????
• ??????????
• ?????????????, ???????????
• ?????????? ? ??????????? ????????
• ????????? ??? ??? ??????
• ????????? ?? ?????? ??????
• ????????? ???????????? ??????

50
?????? ????????

• ??????
• ? ???????? ???? ?????????
• ???????? ????? ??????????
• 2 ?????? (OK?????????)/(Failure)
• ????? ?????? ??? Outcome
• ? ????? ??????????? ??? ? ??? ?? ??????

51
?????? ????????

• ? ??? ?? ??????
• 2 ?????? (OK?????????)/(Failure)
• ???? ?? ?? ????????? ?? ?????, ??? ?????? ?
  ?????? OK, ? ??? ?????? ? ?????? Failure
• ??????? ??? ?????
• ????????? ???????? ???????????
• ??? ?????? ? ???????????, ???? OK
• ??? ?????? ? ???????, ???? Failure
• ??? Continuation-passing style

52
?????? ????????

• ?????????? API
• interface ActionltTgt
• void run(ContltTgt cont)
• interface ContltTgt
• void ok(_at_NotNull T result)
• void fail(Failure failure)
• ??????? ???? ?????????? ???????
• ?????? action() action.run(new ContltFoogt() )
• ?????? foo() bar() ???? ????? ???
• ?? ??? ????? ??????????????
• ????? ??????? ???? ?????????? ????????

53
?????? ????????

• ??????? API
• public class Actions
• public static ltTgt _at_NotNull T run(ActionltTgt
  action) throws ActionFailed
• final T result new T1
• final Failure failure new Failure1
• action.run(new ContltTgt()
• void ok(_at_NotNull t res) result0
  res
• void fail(Failure f) failure0
  f
• )
• if(result0 ! null)
• return result0
• else
• throw new ActionFailed(failure0)

54
?????? ????????

• ?????????
• ActionltAgt justReturn(A a)
• ActionltAgt alwaysFail(Failure f)
• ActionltBooleangt trueAfter(long millis)

55
?????? ????????

• ??????????? ????????? ??????
• ActionltAgt withDefault(ActionltAgt a, A defaultA)
• ActionltAgt orElse(ActionltAgt tryThis, ActionltAgt
  ifFailedUseThis)
• ????? ????
• ActionltAgt withRescue(ActionltAgt a,
  FunctionltFailure, ActionltAgtgt rescue)
• ActionltAgt withTimeout(ActionltAgt a, long timeout,
  Failure onTimeout)
• ActionltAgt withFinally(ActionltAgt a, Runnable
  finalizer)
• ActionltAgt withRollback(ActionltAgt a,
  CallableltFailuregt rollback)
• ActionltAgt withRetry(ActionltAgt a, int nAttempts,
  long waitIntervalMillis)

56
?????? ????????

• ??????????? ????????????? ? ???????????
• ActionltAgt asynchronously(ActionltAgt a) // Cont
  ?????? ?? ?????? ????
• ActionltAgt earliestOf(ActionltAgt rivals)
• ActionltAgt awaitAllOf(ActionltAgt actions)
• ActionltAgt after(long delay, ActionltAgt a)
• ActionltBgt parFold(Function2ltA,B,Bgt reducer, B
  seed, ActionltAgt actions)

57
?????? ????????

• ??????????? ??????????????????
• ActionltBgt then(ActionltAgt first,
  FunctionltA,ActionltBgtgt second)
• ???????? ???????? ????????? ??????. ??? ??????
  Cont.
• return justReturn
• (gtgt) then

58
?????? ????????

• ???? ??????????
• public static ltA,Bgt ActionltBgt then(ActionltAgt
  first, FunctionltA,ActionltBgtgt second)
• return new ActionltBgt()
• public void run(final ContltBgt cont)
• first.run(new ContltAgt()
• public void ok(A a)
• second.apply(a).run(cont)
• public void fail(Failure f)
• cont.fail(f)
• )

59
?????? ????????

• ???? ??????????
• public static ltAgt ActionltAgt earliestOf(ActionltAgt..
  . rivals)
• return new ActionltAgt()
• public void run(final ContltAgt cont)
• final CountDownLatch latch new
  CountDownLatch(1)
• class Hook implements ContltAgt
• private boolean arrived false
• private Failure someFailure
  null
• private int failures 0
• public void ok(A res)
  if(arrived()) cont.ok(res) done()
• public void fail(Failure f)
  if(failed()) cont.fail(f) done()
• private void done()
  latch.countDown()
• private synchronized boolean
  arrived()
• return arrived ? false
  (arrivedtrue)

60
?????? ????????

• ??? ???? ????????????
• ?????????? ??????? ????????? ? ?????????? ??????,
  ????????????? ?? ?????? ?? 3 ???? ? ????? ??
  ?????? ??????? ?? ????? 25 ??????.
• ActionltPagegt simplyFetch(String url)
• return ...
• try
• cont.ok(pageFetcher.fetch(url))
• catch(Exception e)
• cont.fail(new Failure(e))
• ActionltPagegt asyncFetchMirrorsWithRetry(String...
  urls)
• ListltActionltPagegtgt retriers newList()
• for(String url urls)
• retriers.add(retry(
• withTimeout(simplyFetch(url), 25000,
  new PageTimedOut(url)),
• 5000, 3))

61
?????

• Java ????? ???? ??????????
• ?? Java ????? ?????? ? ?????????????? ?????
• ???? ????? ?? ????? ????????? ??????? ??
  ?????????
• ??????? ???? ?????????? ???????
• ?? ?????????????? API ??? ?????????? ????? are a
  good thing
• ??? ????????? ????????????? ???? ?? ?????
• ??????? ???? ?????????? ????????
• ??????
• ??????????
• ??????? ?????????? (80 ????? ? ?????????
  ?????)
• ???? ?????????? ???? ??????, ? ??????? ?????
  ???????????
• ???? ??????? ??? ??????? ???? ???

62
???????!

• ????????